Carabiners are incredibly strong used correctly. However, it is worth being aware of ways that carabiners can interact with bolts that will dramatically compromise their integrity, and how this feeds into their design.

Hooking-up on the more traditional style of bolt is an example of this: where the square edge of the hanger gets caught in the notch of the nose and sits there in a weakened cross-loaded orientation.

A clean nose design with a steep top bar can't hook-up in the same way as with some biners that have a notch in the nose. Carabiners such as the Shadow, Alpha Sport and Alpha Trad, that feature in the video, will slip back into the correct orientation, with the gate closing when a load is applied. If the biner stayed hooked-up, then not only is the gate open, but the load is well away from the major axis. Tests with an 85 kg dynamic load and a .85 fall-factor showed carabiners failing in this scenario at between 3.2 - 4.1 kNs.

This is one of the reasons why all of DMM's sport climbing biners feature a clean nose and our wire gate trad orientated biners are made with a clean nose or as small a notch as possible. The Phantom, for example, has a minimal notch in the nose making it actually quite difficult to hook-up. A carabiner should ideally be loaded along the back-bar with the gate closed. Unsurprisingly, among the Phantom, Spectre 2 and Thor, the latter with its high gate-open rating (11 kN) and extra security, performed best in both the static and dynamic tests.