ISC
SH903

Because the hook in a gated hook suspends the entire load, the spine and basket must be larger and stronger than in a carabiner with the same strength rating. Steel is an excellent material for industrial snap hooks due for the wear resistance and strength. If made from aluminum, they would be weak or bulky.

Unlike many traditional snaphooks, the gate latch in carabiner snaphooks is designed to be loaded, making it a carabiner rather than a gated hook (in which the gate does not bear a load). When forged from aluminum, the result is a lighter connector - but with another point of potential failure from the gate.

The SH903 is one of the earliest aluminum carabiner snaphooks (gate loading, palm squeeze lock, captive eye), with a secondary lock. This lock, described as the "third action catch" by ISC, must be depressed before opening the palm squeeze lock

("second-action keeper"). Rollout is a serious issue with palm squeeze locking connectors, and a secondary lock (third action) helps mitigate that risk - in theory at least:

Unfortunately, the stamped sheet metal components of the catch and the keeper can bend and allow them to slip past each other. This can cause the gate to operate as a as a single-action connector (non-locking) or, become stuck in the open position (zero action? Horrifying).

After a video of the failure occuring at height (no injuries) sparked significant discussion amongst arborists and others, ISC did issue a "User Inspection Notice" on the issue.

This particular example (retired from use at height) does exhibit the deformed (splayed out) palm squeeze keeper, and will occasionally fail - sliding over the catch on one side, and under on the other. Even when the locking pieces block each other correctly, the palm squeeze can be moved far enough to permit the gate to open past the point of latching with the nose - reducing the major axis strength to the gate open strength. It is unclear if this amount of movement would occur when the unit was brand new.

As perhaps further evidence of the hard life this connector has lived, this example has a notible bend of the eye to the left (up when carabiner facing gate left).