Continually check the state of your equipment

Safety equipment wears and become unsafe. An example is the wire gate carabiner (Kong Argon wire) in this photo.

The wire gate should close it self completely, but in this case it sometimes stays open. The open gate rating of a carabiner is much lower than a closed one (usually about 1/3 of the closed strength) and obviously rope or slings can slip out more easily from an open gate.  

This carabiner comes from a quickdraw. A set up two carabiners with a sling used for lead climbing in sport/alpine climbing. A failure of the carabiner or the unclipping of this carabiner could end up in very painful experience if not death.

This carabiner is actually fairly new and has little wear on it. This highlights why it’s important to continually check the state of your equipment. The exterior look might give a good indication, but it does not have to be.