Locking carabiner

A locking carabiner has a sleeve, twist, or automatic mechanism over the gate so it cannot be pressed open by an accidental bump against rock, gear, or another carabiner. That extra security is why locking carabiners are used at points where an open gate would be dangerous, such as attaching a belay device to a harness, building an anchor, or rappelling.

Locking gates come in a few styles: screw gates that you twist closed manually, auto locking gates that close on their own when released, and magnetic or twist lock variants that aim to combine speed with security. Shapes vary too, from pear shaped HMS carabiners that give a belay device room to move, to smaller D shaped lockers for anchors.

Always check that a locking carabiner is actually locked before weighting it, since a carabiner left on the verge of closed can still fail under load. Cross loading, where force is applied across the minor axis instead of along the spine, also weakens a carabiner significantly, so pay attention to how it sits when clipped into a belay loop or anchor.