Placing Trad Protection: Nuts, Cams, and the Three Conditions of a Good Placement

🌏 中文版

Open the Defulan crag page on nobodyclimb and look at a 5.11b called Miruku. The protection field says only "需小號cam, nut": needs small cams and nuts. There are no bolts on the route, only an anchor at the top.

To climb it, you place every piece of protection yourself. This post covers three things: what holds a nut and a cam in place, how much the standards require them to hold, and how to judge a placement. By the end you should be able to name the three conditions of a good placement and read the gear notes on a route.

The previous post, Grades and Protection Ratings, covered R and X ratings: what a fall means when protection is sparse or poor. This one is about the protection itself.

To be clear up front: this post does not replace a course. Learning to place gear takes someone standing next to you, pulling on your pieces and pointing out problems until your eye is trained.

Two kinds of protection: nuts wedge, cams push

Nuts: wedged where the crack narrows

A nut is a metal wedge, wider at the top than the bottom, on a wire cable. You find a section of crack that narrows downward, slot the nut in at the wide part, pull down, and it locks in the narrow part. Hexes belong to the same family; the official UIAA pictorial for EN 12270 / UIAA 124 draws both a tapered wedge and a hexagonal one.

Nuts have no moving parts. They are cheap, light and durable, but they only work in one kind of terrain: the crack has to constrict. AMGA Certified Rock Guide Elaina Arenz, writing in Climbing, puts the division plainly: cams in parallel-sided cracks, passive gear in constrictions and V-shaped cracks.

Watch it: HowNOT2 placed a handful of nuts in Hawaiian granite and hauled on them with a pulley system until something broke. Start at 0:35 with a BD Micro Stopper: it stayed locked in its constriction, and the wire finally snapped at about 9 kN. Each nut was pulled once, slowly, not shock-loaded by a fall; what it shows is that a nut seated in a good constriction holds, not that any small nut jammed in anywhere will.

Cams: turning a downward pull into outward pressure

A cam has two to four lobes on an axle. Pull the trigger and the lobes retract; put it in a crack, let go, and the springs open the lobes against both walls.

The Wikipedia entry on SLCDs explains why it holds: the lobes are logarithmic spirals, so the angle between lobe and rock stays the same no matter how far the lobes open. When a fall pulls the rope down, that constant angle turns the pull into outward pressure on the rock, which creates a lot of friction, and the cam stays put.

That angle is the camming angle, and it differs by design:

• The original design Ray Jardine invented in 1978 and sold as "Friends" used 13.75°.
• UKClimbing's review of the BD Camalot C4 gives the C4 as 14.5°, slightly above the "industry standard" 13.75°: a bit more range per unit, but marginally less camming force when over-cammed or tipped out. The reviewer adds that neither effect is worth getting excited about.

As a climber, remember the angle as "roughly 13–15°, varies by brand." What matters more is the other half: a cam pushes force into the rock. If the rock is loose, chossy, wet or dirty, even a textbook-looking placement can break the rock or rip out. Both Wikipedia and Arenz put "solid rock only" first.

Watch it: in What breaks first?, HowNOT2 plugs the camming angle into a formula to work out how hard a cam pushes on the rock. At common angles, the outward force comes to roughly twice the downward pull. The stretch from 0:40 to 1:20 is a deliberate parody of academic jargon and safe to skip; the later home-built rig gets ratios close to the same figure, but with few samples at low loads, so treat it as an order of magnitude.

Something to do tonight: take a cam, pull the trigger all the way, then let it open slowly and watch how the lobes move. Put it in a door gap or between two books and pull down on the stem. Feel which way the lobes push.

How much the standards require them to hold

Personal protective equipment sold in Europe needs CE certification, and nuts and cams each have a standard. The official UIAA pictorial sums them up on one page:

Both standards require the manufacturer to mark the guaranteed minimum strength in kN on the piece. That is the key point: 5 kN and 2 kN are floors, not the number on the piece in your hand. Black Diamond's QC Lab says it directly: CE-certified cams are rated 5 kN, but most are over 10 kN.

The marked rating is itself conservative. Another BD QC Lab explains that ratings start from a three-sigma calculation: the mean of many break tests minus three standard deviations, so 99.7% of failures happen at a higher load.

Watch it: HowNOT2 visits Black Diamond's lab and talks to the cam design engineers. From 11:00, they explain that CE strength testing is only a small part of their cam test plan; most of it is fatigue and environmental testing, such as cyclic loading, heat, ice water and pulls over edges. That is the manufacturer's own account. The same stretch calls the expiry date on a cam a conservative estimate and says heat, water and salt deserve extra caution. Some of the old cams pulled in the first half had been through a house fire and were tested only once or twice each, so they say nothing about whether old cams are still fit to use.

So how much force does a real fall produce? Petzl tested with real people: an 80 kg climber falling just after leaving a multi-pitch belay (fall factor 1) put about 6 kN on the redirect point. Petzl's note: no problem for a solid fixed anchor, but critical on a dubious point such as a small wire.

That makes "needs small cams, nuts" a warning. Small pieces can be rated much lower: BD's smallest Z4 #0 is rated 5 kN, while a mid-size #1 Camalot is rated 14 kN. The smaller the piece, the more precise the placement has to be.

Something to do tonight: turn over every cam and nut you (or a friend) own, find the kN marking, and write down the lowest number.

Three conditions of a good placement

After placing a piece, ask three questions.

1. Is the rock solid?

Check the rock before the gear. Arenz's warning signs are loose, chossy, wet and dirty: in rock like that, a good-looking placement can still break the rock or pull out. A cam pushes force outward into the walls, so this matters even more for cams.

Watch it: HowNOT2 pulls Metolius TCUs out of granite cracks in California's Sierra. Start at the 5:25 slow-motion clip: the cam doesn't slip at all; the whole block of rock is what moves. The video description records the weakest pull slipping at about 5.5 kN. These were the same worn TCUs pulled repeatedly by hand, and the numbers vary widely, so they are not a strength figure for the cam. The point is a placement that looked fine while the rock gave way first.

2. Is it the right size?

Cams: Arenz recommends lobes retracted between 50 and 90%. The lobes need room to keep expanding in the crack to give the most holding power.

BD's testing fills in both ends:

• Too little retraction (lobes nearly fully open, "tipped out"): BD calls 25% retraction a sketchy placement. Micro cams tend to have their lobes invert and rip out; very large cams tend to have their lobes buckle.
• Too much retraction ("over-cammed"): BD says the closer a cam is to 100% retraction, the stronger it is; the common belief that a fully retracted cam is weaker is not true. The downside is that it may get stuck.

Nuts: the nut has to go in at the wide part and lock in the narrow part when pulled down. If the narrow part is wider than the nut, it pulls through.

Watch it: in Totem Cams TESTED!, HowNOT2 first sets up a deliberately marginal placement with only two lobes touching rock; it pulls out at about 2 kN. The same model in a good horizontal crack, loaded correctly, holds until the sling breaks. Totems are built differently and can hold on two lobes, so the results don't transfer directly to ordinary cams, and each placement was pulled only once or twice, slowly. The takeaway: with the same piece, the gap between a good and a bad placement dwarfs anything the rating tells you.

3. Is it aligned with the pull?

The direction of load is the direction the rope pulls on the piece in a fall: usually down, sometimes out when you are near the rock.

• Cams: Arenz wants the stem angled down toward the anticipated pull. If the stem sticks straight out of the rock, the cam will twist and shift under load and may fail. BD tested large cams set about 30° off the line of pull and found large cams lose strength off-axis more readily than small ones.
• Nuts: they only hold when pulled toward the constriction. Pulled the other way, upward, they can come loose; when Arenz teaches seconds to clean nuts, the first step is a sharp upward tug on the sling. So if the rope above a nut will pull it up or out, extend it or use a cam instead.

Something to do tonight: write the three questions on a card. Next time you second and clean gear, say them for every piece: rock, size, direction.

Walking and extension: the rope keeps pulling after you place it

A well-placed cam can turn into a bad one after you climb past it.

Arenz warns that the lead rope tugging on pieces can make them "walk" out of their placements. The fix is to keep the rope running as straight as possible, clipping a quickdraw or alpine draw to placements where needed.

BD's guide to a first trad rack agrees that apart from straight-in splitters, most trad routes need extended placements to reduce rope drag. It suggests six to eight alpine draws to start: a 60 cm sling with two carabiners.

Arenz also gives two rules for placing gear on lead:

• Make the first piece a cam if you can. Cams can take downward, outward and upward pulls. If the first piece fails, the rope angle can pull the pieces above it out one after another, called zippering.
• Place gear about one body length apart. When your last piece is at your feet, place the next one.

Something to do tonight: next time you lead in the gym, watch the line the rope takes from you to your belayer. Which quickdraw makes the rope bend sharply? If that were a cam, which way would it be pulled?

Reading the gear notes on a route

Back to Defulan. The nobodyclimb route data lists the gear for most trad routes in the protection field. A few examples:

The numbers are BD Camalot sizes. BD's guide says a standard rack of cams is one of each size from .2 to #3, and recommends adding a set of nuts. Read that way, "single rack to #2" means one of each size, topping out at #2. Usage varies by area, so asking someone who has climbed the route is the most reliable check.

Read the description too, not just the protection field. On the same crag, South Heaven Gate (南天門) lists "at least one #5 and one #6," and the next line says "please don't climb it, lots of rockfall." Defulan's crag description also warns that some areas have unstable rock and frequent rockfall, so wear a helmet when climbing and belaying. The right gear does not help on the wrong rock.

Course gear lists in Taiwan are another reference. Adventure Taiwan's single-pitch trad course uses BD C4 #.4 to #3, one each, Stoppers #5 to #11, one each, and a nut tool.

Something to do tonight: pick three trad routes at Defulan or Long Dong on nobodyclimb, copy their protection fields, compare them with the gear you (or your partner) own, and mark which pieces are missing.

How to start practicing

Arenz lays out a progression where no step requires taking a lead fall:

1. Place gear on the ground: find a crag with cracks at the base and place as many pieces as you can, checking each against the three conditions.
2. Second and clean: follow someone experienced. Before touching a piece, look at how it was placed, then reverse it. For cams, pull the trigger and ease it toward the wider part of the crack; for nuts, tug upward first, and if it does not come out, push it up from below with a nut tool.
3. Mock lead: tie into two ropes, a top rope and a lead line, and place gear and clip the lead line as you go. Keep a little slack in the top rope so you can weight each piece; if it fails, the top rope catches you.
4. Live lead: drop the top rope and place and clip on your own.

The trad courses at Adventure Taiwan and Wild Lily Rocks both hold their outdoor sessions at Long Dong and both require lead skills before you sign up. Adventure Taiwan teaches the "S.T.A.R.S." placement principles; Wild Lily Rocks has you place protection over and over and judge your own placements.

Something to do tonight: ask your lead partners whether anyone climbs trad. Next time they go to Long Dong, ask to second and clean their gear.

Practice: four scenarios

The answer is under each question; think first, then look. For more questions, try nobodyclimb's rope-system practice: trad protection.

1. A parallel-sided, hand-width crack. You have nuts and cams. Which do you place?

2. You place a cam and the lobes only touch the rock when nearly fully open. Clip and keep climbing?

3. A cam sits in a horizontal crack with the stem sticking straight out. You are about to clip a quickdraw directly to it.

4. The route note says "single rack to #3," and you only have .3 to #2, one each, plus a set of nuts.

Next

Once you can place single pieces, the next question is: at the top of a route without bolts, how do you combine several pieces into an anchor that two people can hang on? The next post, Building Anchors, covers redundancy, load distribution, no extension, and how much force an anchor actually sees in a fall.

If you have not read the series overview, start with Sport vs Trad Climbing.

Further viewing: gear-testing and instruction channels

Every video embedded above comes from HowNOT2; Hard Is Easy is another channel built around gear and belay experiments. Both are good places to keep digging, as long as you keep each channel's limits in mind.

• HowNOT2: run by Ryan Jenks. It started in 2016 as highline safety instruction and grew into breaking climbing, caving and canyoneering gear, plus the Bolt Busters series that pulls bolts out of real rock. Its value is in the cases beyond the rated number: knots, wear, old gear, bad placements. Limits: most tests are slow pulls on a home-built rig with one to three samples, and Ryan himself calls it entertainment, not science; the channel is backed by an online gear shop, and some tested items are sold there.
• Hard Is Easy: run solo by a climber who signs as Ben, a former software developer. After watching a hard catch slam a climber into the rock in Tonsai, Thailand, he designed his first experiment; the channel now focuses on experiments and physics explanations about belaying, ropes, carabiners and belay devices, with several recent episodes filmed in Mammut's lab. Limits: most experiments are his own design, not EN/UIAA standard tests.

Update Log

• 2026-10-23: Added gear-testing videos from HowNOT2, Hard Is Easy and similar channels, plus a channel guide

References

• Gym to Crag: Trad Climbing (Elaina Arenz, Climbing, 2019)
• EN 12276 / UIAA 125 Frictional Anchors pictorial (UIAA)
• EN 12270 / UIAA 124 Chocks pictorial (UIAA)
• QC Lab: The Beauty and Limitations of Big Cams (Black Diamond)
• QC Lab: Sling Strength in 3 Anchor Configurations (Black Diamond)
• How to Build Your First Trad Rack (Black Diamond)
• Forces at work in a real fall (Petzl)
• Spring-loaded camming device (Wikipedia)
• Review: Black Diamond Camalot C4 (UKClimbing, 2019)
• Defulan route data (nobodyclimb)
• Adventure Taiwan: Single-pitch trad climbing (in Mandarin)
• Wild Lily Rocks: Single-pitch trad full course (in Mandarin)
• nobodyclimb rope-system practice: trad protection
• Grades and Protection Ratings
• Building Anchors