Finger Cracks: Thumb-Down Locks, Knuckle Constrictions, Pin Scars and Your Feet

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Follow a hand crack up and it often narrows until only your fingers fit. That is where many people first find crack climbing frightening: you push the thinnest parts of your body into the rock, twist them, and hang your whole weight off them.

This is post 3 of the Crack Climbing Technique series. The shared principles of jamming are in the crack-climbing primer, hand jams in Hand Cracks; foot jams are in post 2, Foot Jams. This post covers finger-width cracks. First the widths, then the thumb-down lock, when to switch orientation and how to find spots where your knuckles lock; the second half covers pin scars, where your feet go, and when to stop jamming and layback. Off-fingers, where fingers rattle and hands won't fit, and ring locks are left for post 4 (in progress).

By the end you should be able to look at a finger crack, tell which of three widths it is, and pick the right lock.

Three widths: tips, good fingers, rattly fingers

In the book Crack Climbing, Pete Whittaker compares a ballerina and a lumberjack at the same thin crack (Climbing.com runs an excerpt). The ballerina's fingers lock with ease while the lumberjack can't fit a single finger in; widen the crack a few millimeters and the roles reverse. Whittaker says one millimeter can be the difference between a move feeling easy and impossible.

So don't read finger cracks by cam size. Read them by how deep your fingers go:

VIDEORACLES' finger-lock lesson runs from the thinnest size to the widest in three minutes:

• 0:31: a very thin crack, so pinkie down, since the pinkie and ring finger are the thinnest.
• 0:49: a little wider, so thumb down; with the first knuckle locked you can hang on a straight arm and place gear.
• 1:19: the same with the second knuckle locked.
• 1:41: the rattly width, where the lock comes entirely from torque. Jean-Pierre Ouellet, quoted by Climbing.com, also says you can "cheat" on a rattly jam by pushing your thumb against the edge of the crack.
• 2:05: into ring locks, which is the next post.

The Japanese climber Niwaka Alpinist gives a Camalot scale for their own fairly thick fingers in the blog post Sekai wa sore o finger crack to yobunda ze (in Japanese): at #0.4 the fingers go in to the base, the easiest size; at #0.3 the second knuckles of the index and middle fingers won't go in, though the pinkie side goes a little deeper, and the more you twist the better it holds; #0.5 is "narrow, yet loose", which the author calls the nemesis of finger cracks, needing a thumb technique (covered in the off-fingers post). Below #0.2 you mostly get fingertips only. That is a thick-fingered scale, and the author asks readers to translate it to their own fingers.

Something to try tonight: take your own cams, a friend's, or the gym's rental cams, open #0.3, #0.4 and #0.5 to mid-range, and test them against your fingers: which one goes in to the base, which only to the first knuckle, and which goes in but wobbles. Save it on your phone; those are your three finger-crack widths.

Thumb down: the most common and strongest finger lock

For the good-finger width most people go thumb down. Whittaker's steps from the excerpt, condensed into four moves:

1. Turn the hand thumb down, pinkie up, elbow out. The back of your hand faces you, as if saluting. Bend at the wrist so the fingertips point at the crack, fingers relaxed.
2. Slide the fingers in to the base, thumb outside the crack. Flatten the palm and forearm against the rock.
3. Rotate the elbow and forearm down until they line up with the crack. Imagine a metal rod through your forearm so the wrist can't bend. As you rotate, the index and middle fingers bite; the ring finger often rotates out and stacks on the front two, and the pinkie comes out against the crack wall. All of that is correct.
4. Pull down, not out. Once the palm and forearm leave the rock you are pulling outward and the lock weakens.

If your index finger is slightly too fat or already sore, Whittaker's variation is to leave it out and make the middle finger the bottom finger.

VIDEORACLES stresses the same thing: elbow toward the midline, pull straight down. Climbing.com's nine tips pass on advice from finger-crack master Jean-Pierre Ouellet: keep your elbows toward your rib cage whatever lock you use, and relax your hands instead of over-gripping; the jams hurt less and you pump out less.

Korean climbing guide Kim Jong-sik (K Climbing Company) covers finger jams from 1:49 in 12 Jamming Techniques (in Korean) and says thumb-down is the stronger lock. Embedding is disabled, so watch it on YouTube.

Something to try tonight: leave a finger-width gap between two books on a shelf and run the four moves ten times: salute, slide in, rotate the elbow down, pull down. After each rotation, check that your palm and forearm are still on the books and that your ring finger and pinkie came out on their own.

Thumb up, pinkie down: when to switch

Thumb down isn't the only answer. There are three reasons to switch:

The crack is too thin. If index and middle fingers won't fit, flip to pinkie down, thumb up, and use the thinnest fingers. Whittaker says this lock twists less, so without a constriction it can feel like it's slipping and be very strenuous; find a constriction where the pinkie jams passively and it can be better than holding a massive jug. Twist gently from the wrist, like a tricky lock, and wait for it to click into place rather than forcing it.

You need reach. Ouellet calls jamming thumb-down all the time a rookie mistake; thumb-up can give you the extra reach to the next jam.

You want to shuffle instead of crossing. Lower hand thumb-up around chest height, upper hand thumb-down, can be easier than alternating the high hand. Leaning cracks work the same way: if the crack leans left, lead with the left hand thumb-down and follow with the right hand thumb-up (Climbing.com).

Sources disagree on which should be your default. Kim says thumb-down is stronger: when your body is right of the crack, right hand thumb-down and left hand thumb-up; facing the crack straight on, both thumb-down. Ouellet lists always-thumb-down as a rookie mistake. A reading that fits both: default to thumb-down, and switch to thumb-up when you need reach or are shuffling.

A Japanese climber redpointed Kumo no Ito 5.11c at Ogawayama (ROCKTOPO) and then left move notes in the description, which use 逆手 (gyakute) and 順手 (junte) to tell the two hand orientations apart. On the upper crux: right hand gyakute finger lock, thumb resting lightly, pinkie pulled out; left hand junte finger lock, pressed down into the crack to make it stick. That gyakute description, thumb resting and pinkie pulled out, is close to Whittaker's thumb-down finger lock, where the little finger comes out of the crack. ROCKTOPO tags it as one of Ogawayama's three great cracks. The video has no subtitles, so watch the hands alongside the notes.

Something to try tonight: in the same book gap, pull down thumb-down for ten seconds, then flip to pinkie-down for ten. Use arm strength only; don't hang your body weight on the books. If you have a gym crack, hang each for ten seconds with your feet on the wall. Compare: which needed more torque, and which let you hold your hand higher.

Find the constriction: let your knuckles lock like a nut

Whenever you put a body part in a crack, look for constrictions to jam passively first, so you don't have to twist (Whittaker). Climbing.com is blunter: your knuckles act like nuts wedging into constrictions; it takes very little muscle, and you feel like you could hang forever.

So on a finger crack, scan for places that are wider above and narrower below. Put your fingers just above the constriction and pull down; the knuckles seat in the narrow part. That is what VIDEORACLES' first- and second-knuckle demos show: with the knuckle locked you can hang on a straight arm and place gear, and torquing the elbow only adds force.

Now and then a crack has a noticeably wider pocket, a pod, often the only rest on a finger crack. The video below follows Mary Eden on Pat's Blue Ribbon at Indian Creek (Mountain Project rates it 5.13-), a steep finger splitter with a pod and a crux from the pod to the arête. From the embed's start point, the climber in the video explains the sizes: leaving the pod the crack pinches quickly from #0.3 to #0.2 and smaller, and a blue Metolius is already tips for the climber's hands.

Something to try tonight: on a gym crack or any photo of a crack, trace it upward with a finger and mark only the spots that are wider above and narrower below. You'll find fewer constrictions than you expected, and they are the route's handholds.

Pin scars: pockets left by old pitons

In 1972, Yvon Chouinard and Tom Frost opened the Chouinard Equipment catalog with A Word…: hard steel pitons hammered in and pulled out again and again were turning the cracks of popular Yosemite routes into series of piton holes. Those pockets are pin scars. In the same essay the two announced their switch from pitons to chocks and made the case for clean climbing.

For finger-crack climbers today, pin scars are ready-made constrictions. Climbing.com says pin scars and pods give wider spots directly above constrictions, which lock fingers excellently. The costs are two:

• Gear is hard to place. The scars flare and are shallow, so cams sit poorly.
• They wreck your feet. Toes jammed into scar after scar hurt by the top.

Serenity Crack in Yosemite (5.10d, 3 pitches) is the best-known example. The Mountain Project page describes pitch 1 as hundreds of blown-out pin scars the size of #1 Camalots forming a practical ladder, with no secure gear for a long way, and painful on the toes. Commenters disagree about offset cams: some say they work very well, others that the scars are too flaring or too shallow; one climber finally got a cam in, only for it to block a good foothold for the next move.

Brant Hysell's channel filmed a day on the route. From 7:34 the leader explains that it's a straight-up crack, but every piece gets a sling because the placements are all in pin scars and might walk.

Something to try tonight: pause a pin-scar ascent video (this one works) at each pocket and note whether the climber's fingers sit in the top of the scar or on its lower edge, and whether the feet go into the scar or beside it.

Feet in finger cracks

Climbing.com says the secret to finger cracks is still in the feet, you just have less to work with: unless your feet are tiny, you jam just your toe tips, smear the edges of the crack, or find holds on the face.

Face holds first. Ouellet says the tiniest bumps will be good enough to get to the next jam. VIDEORACLES' footwork lesson also puts them first: a hold outside the crack, or a low-angle slab you can smear, beats anything in the crack. The Japanese thick-fingered author finds a toe jam barely sticks at #0.4 and is hard at #0.3, so looks for offsets or face holds first and smears on the crack only when there is nothing else.

When the face is blank, Whittaker gives three techniques in the newsletter 3 Secret Weapons for Finger Cracks:

1. Toe jam. Turn the foot to its thinnest dimension, mostly by twisting the ankle; put the big toe in first and use it as a pivot to roll the shoe's pinkie-toe edge into the crack; add a small ankle twist, then actively dig the toe into the crack edge. Whittaker says a weighted foot never slips. For slightly steeper or wider cracks.
2. Front-on smearing. Foot facing the crack, toe on the crack edge, drop the heel as you stand to maximize rubber on both edges. For pin scars, pods, flares, or a slight corner.
3. Frogged position. Feet high under your bum in their thinnest dimension, knees out, each foot pushing outward on the opposite wall without twisting; drop your bum toward your heels and shuffle in small steps without crossing. For very parallel cracks where twisting just rolls the rubber out.

From 0:30 in VIDEORACLES' footwork lesson you can see the second technique: shoe point lined up with the crack, heel dropped, knee and hip over that foot, the other foot flagged for balance.

Shoes matter too. Climbing.com recommends soft, sensitive, tight-fitting shoes with thin toes; the Japanese author switches to face-climbing shoes on cracks of #0.2 and below, since toe jams are basically impossible there and the feet stay on the face. For foot jams in hand-size cracks see Foot Jams; this post is the reference for the three finger-crack foot techniques.

Something to try tonight: find a finger or thin crack at the gym and top-rope it three times, one foot technique per lap: face holds only, then front-on smears only, then toe jams only. Note which lap was easiest on your hands.

When to stop jamming and layback

Finger cracks often sit in corners where one side of the crack sticks out further. Then you can skip the jam: pull back on the protruding edge with both hands and push your feet against the other wall. That's a layback.

VIDEORACLES opens its layback lesson by calling it not a first-choice technique: it costs a lot of energy, and it's hard to place gear or see how good the placements are. Jam and get weight onto your feet when you can; layback when the flake tilts back too far to jam. Once you commit, keep your feet high and keep moving.

Kim uses a left-facing corner crack on Seoninbong in Crack Climbing Technique Part 3 (in Korean, with creator-uploaded English subtitles); Kim estimates it at about 5.10c. From 6:08 the video lists the conditions:

Kim also compares the two: jamming hurts, but you are less likely to fall. A layback is held by hands and feet pulling against each other, so if one slips you come off; when jamming, each hand and foot is locked on its own, so if one slips the others can still hold you. Laybacking is faster and more energy-efficient. The conclusion is that staying on is worth the pain. Kim adds that layback is a whole-body posture while jamming is a way of gripping, so they were never truly an either-or, just a convenient way to talk. Embedding is disabled on this video too.

On real rock it's often jam, layback, jam again. The Kumo no Ito notes describe the lower crux as a right-hand gyakute finger lock and a left-hand thumb technique (covered in the off-fingers post), then a foot jam, the right hand moving up, and a transition into layback. The Korean climber 쏘맥 클라이머 (Somaek Climber) tried the Seoninbong South Corner Crack (코너크랙) 5.10d and wrote the attempt up in the description: after the stemming section, at the moment of committing to the crack, nerves broke, a foothold went unfound and a foot slipped; later, fingers bleeding but no longer hurting, the layback moves started to flow.

How to layback is covered in the layback, corners and leaning cracks post (in progress).

Something to try tonight: next time you meet a corner crack at the gym, ask three questions on the ground: will a jam stick, is the edge good to grip, how steep is the wall? Decide jam or layback, then afterward ask whether the call was right.

Big hands and small hands

The series overview explained that the same crack is a different size for different hands; Whittaker also calls finger cracks one of the most fickle sizes. His 2026 newsletter puts it this way:

• #0.3 and #0.4: smaller fingers lock effortlessly; bigger hands struggle to get as much skin contact.
• #0.5 (purple): a larger hand finger-jams comfortably; a smaller hand often has to ringlock.

Whittaker's golden rule: unless you can't get a fingertip past the first joint, there is always a crack technique you can use; some are just harder than others.

Thick fingers aren't hopeless either. In another post (in Japanese) the same Japanese author says a finger lock works as long as your finger goes in to just past the first knuckle, and routes thinner than that are a minority. The author also flags a detail: two wraps of tape make a finger about 1 mm thicker, and in a 2 cm finger crack that millimeter matters. Think before taping if your fingers are thick.

The author's YouTube channel of the same name filmed B1 Finger at Mizugaki (ROCKTOPO lists it at 5.11a). The description calls it a short, technical finger crack in an all-trad, no-bolt area, a good gateway to 5.11.

Small hands often have the edge in finger cracks. Hazel Findlay says in 10 tips for short climbers that smaller hands and feet can help in crack climbing, and some cracks are simply easier with small hands. On Long Dong's bolted Finger Crack in Music Hall (Mountain Project lists it at 5.11), a commenter likewise says small fingers make the crux far easier.

Something to try tonight: compare your three widths with a friend whose hands are bigger or smaller than yours. For the same cam, which width is it for each of you? Next time you climb together, ask for their scale before copying their beta.

Practicing finger cracks in Taiwan

Mountain Project lists several Long Dong routes with finger cracks, a good place to start:

• Fillet Show 5.8: a clean finger crack in the back of a dihedral, with slightly finicky gear; the belayer stands on a narrow platform above the waves, so build an anchor.
• Grotto 5.10b: in the Second Cave, a crack that quickly thins to fingers and then to tips, climbed on hand jams and smearing feet.
• Finger Crack 5.11: the rightmost bolt line in Music Hall, a bolted finger crack where you can leave the rack at home and focus on the locks.

On a bolted finger crack you can practice hands and feet sport-style without also managing gear. To lead finger cracks at Long Dong, read Trad Protection and Choosing Cams first; finger cracks take the smallest cams.

Something to try tonight: open the Mountain Project pages for the three routes above, check the cam sizes in photos and comments against the three widths you measured in the first section, and pick the one that is "good fingers" for you.

Practice: five scenarios

Answers are under each one. Think first, then look.

1. Your index and middle fingers only go in to the first knuckle, and they slide out when you rotate thumb-down.

2. Your thumb-down lock feels like it's coming out as soon as you pull up.

3. A finger crack leans up and left, both your hands are thumb-down, and you keep falling short of the next lock.

4. A Yosemite 5.10 pin-scar finger crack: the locks are great, but you're nervous the whole way.

5. A finger crack in a corner: the edge sticks out and is easy to grip, the wall is about 75 degrees, and your fingers barely stick.

Next

A little wider than fingers, when fingers rattle and hands won't fit, is off-fingers. The next post covers ring locks and thumb techniques, for many people the hardest size (in progress). For hand jams go back to Hand Cracks, and for other sizes see the series overview.

References

• The Crack Size Map | Crack Climbing Technique
• Hand Cracks | Crack Climbing Technique
• Foot Jams | Crack Climbing Technique
• How to Climb Cracks: Five Jamming Rules, Which Way Your Thumb Points, and Getting Started at Long Dong
• How to Climb: Expert Advice for Mastering Finger Cracks (excerpt from Pete Whittaker's Crack Climbing, Climbing.com, 2021)
• Nine Tips For Improving Your Crack Climbing (Climbing.com, 2022)
• 3 Secret Weapons for Finger Cracks (Pete Whittaker, Wide Boyz newsletter, 2025)
• A New FA in Kristiansund and the Golden Takeaway (Pete Whittaker, Wide Boyz newsletter, 2026)
• A Word… (Yvon Chouinard and Tom Frost, 1972, on the pin scars left by pitons, republished by Patagonia)
• Sekai wa sore o finger crack to yobunda ze (Niwaka Alpinist, 2025, in Japanese)
• There Was a Time I Thought I Couldn't Climb Finger Cracks Too (Niwaka Alpinist, 2025, in Japanese)
• Crack Climbing: Jamming Fingers (VIDEORACLES, 2021)
• Crack Climbing: Jamming Feet (VIDEORACLES, 2021)
• Laybacking (VIDEORACLES, 2021)
• 12 Jamming Techniques: How to Crack Climb Well, Part 2 (K Climbing Company, Kim Jong-sik, 2023, in Korean)
• Crack Climbing Technique Part 3: Jamming or Layback, Seoninbong Left-Facing Crack (K Climbing Company, Kim Jong-sik, 2023, in Korean with English subtitles)
• Ogawayama Kumo no Ito 5.11c RP (The Climb, 2021, in Japanese)
• Kumo no Ito (ROCKTOPO, in Japanese)
• Pat's Blue Ribbon, 5.13- Hard and Painful Finger Crack Climb (Spencer McKay, 2022)
• Pat's Blue Ribbon (Mountain Project)
• The FORBIDDEN 5.10 in Yosemite Valley. - Serenity Crack 5.10d (The Gravity Lab - Brant Hysell, 2021)
• Serenity Crack (Mountain Project)
• The best climb of my life! Seoninbong South Corner Crack (5.10d), lead attempt (pinkpoint) (Somaek Climber, 2023, in Korean)
• B1 Finger 5.11a, Mizugaki Crack Jigoku (Kyo kara Kimi wa!! - Niwaka Alpinist, 2025, in Japanese)
• Jigoku Area (ROCKTOPO, in Japanese)
• How to be a short climber – 10 tips from Hazel Findlay (Hazel Findlay, 2024)
• Fillet Show (Mountain Project)
• Grotto (Mountain Project)
• Finger Crack (Mountain Project)
• Ogawayama | Japan Crags
• Mizugakiyama | Japan Crags
• Seoninbong | Korea Crags
• Trad Protection: Nuts, Cams and the Three Conditions of a Good Placement
• Choosing Cams