Twist-Lock Modified D Steel Carabiner

A twist-lock modified D steel carabiner is a hard-wearing connector with a self-closing, twist-locking gate and an asymmetric D shape. Steel holds up to rope wear and rough handling better than aluminum, which suits rigging and ground work.

When steel makes sense

Aluminum carabiners are light, which is why climbers like them on the saddle. Steel is heavier but far more resistant to grooving from rope, and it shrugs off being dropped, dragged and thrown in the truck. That makes a steel modified D a good fit for rigging points, lowering devices, haul systems and anchors.

The modified D keeps the load toward the strong spine while opening wide enough for rope eyes and slings. More auto-lockers are in auto-locking carabiners.

Steel also makes sense where a carabiner meets a steel ring, chain or wire rope, since aluminum wears quickly against harder metal. Many crews keep a handful of steel twist-locks in the rigging bag for these jobs and leave the lighter aluminum connectors on the climbing saddle.

Gate checks and inspection

A twist-lock gate should snap shut and lock on its own every time. Check it before every use, and keep sap and grit out of the sleeve. Load the carabiner along its spine, avoid cross-loading and three-way loading, and keep it away from edges that can lever the gate.

Retire a carabiner with a sticky gate, cracks, deep grooves, sharp edges or corrosion. Only use it for life support if it is marked and rated for that and meets ANSI Z133 and the manufacturer's instructions.