What Is a Cam in Climbing? | Crack Protection Explained

You’re tied into the wall, staring at a crack that runs straight up for thirty feet, and there are no bolts. This is where a cam earns its keep. A cam, short for spring-loaded camming device (SLCD), is the go-to tool for protecting cracks during trad climbing. Unlike passive gear that relies on friction alone, a cam uses moving parts to actively grip the rock, which makes it especially valuable in parallel-sided cracks.

How a Climbing Cam Works

A cam works on a simple but clever mechanical principle. You pull the trigger wire to retract the lobes, slide the unit into a crack, then release the trigger. Springs push the lobes outward against the rock walls. When you fall, the rope pulls down on the stem, which forces the lobes to rotate outward even harder against the crack walls. The harder the pull, the firmer the grip.

The typical cam has four lobes (some have three), mounted on an axle at the end of a stem. The stem connects to the rope via a sling, and the trigger wire runs from the trigger bar down the stem to retract the lobes for placement and removal. It’s active protection because the device has moving parts that engage the rock, as opposed to passive protection like nuts and hexes which simply wedge in place.

How To Place a Cam Properly

Placing a cam correctly is straightforward once you get the feel for it. Retract the lobes with the trigger, fit the unit into the crack, then release the trigger so the lobes expand and seat against the rock. The key is using a cam within its intended size range—the span of crack widths it can safely fit. A cam that’s undersized or oversized for the crack won’t grip properly.

Parallel-sided and slightly flared cracks are ideal for cams. When you weight the piece, the outward force transfers to the rock walls evenly. To remove it, hold the trigger and push the stem inward to retract the lobes before pulling the piece out. Check that the cam sits fully seated, with all lobes making contact, before clipping your rope in.

Cams vs. Other Protection: Key Differences

Cams excel in parallel-sided cracks where passive gear struggles. A nut or hex depends on constriction—it needs the crack to narrow to hold. A cam, by contrast, expands to match the crack and holds anywhere within its range. That makes cams the preferred choice for the uniform cracks common on many trad routes. However, cams aren’t universal. Heavily irregular or flared placements may call for other protection, and cams are climbing protection—not belay devices, which serve a completely different function in the climbing system.

Cams entered the climbing scene in the late 1970s with Ray Jardine’s spring-loaded camming device. The design was a revolution: suddenly climbers could protect parallel-sided cracks that had previously been dangerous or impossible to protect safely. Today, cams are standard gear in any trad rack, with the REI expert advice on active protection describing them as essential for crack climbing.

If you’re building a rack or replacing worn gear, a solid cam set is the backbone of your protection. Our tested guide to the best climbing cams breaks down the top performers and which sizes to start with.

Is a Cam the Right Protection for Your Climb?

You’ll use a cam when you’re climbing a route with cracks and no fixed bolts. It’s the primary protection for traditional climbing. The trade-off: cams require practice to place quickly and confidently, and the fit matters. A poorly placed cam can pull out under load.