Aventail

Flexible curtain of mail attached to the skull of a helmet

An aventail or camail is a flexible curtain of mail attached to the skull of a helmet that extends to cover at least the neck, but often also the throat and shoulders. Part or all of the face, with spaces to allow vision, could also be covered. Some featured a ventail which could be folded over the bottom face and vice versa, much in the same manner as a visor.

This keyword could refer to multiple things. Here are some suggestions: