An aventail is a defence for the neck of a combatant. This defence might be of mail, metal strips or plates or it might be only of leather or cloth depending on the wealth of the wearer, the period or the culture.
Aventail is also used to describe a mail drape (often padded) that was attached to a bascinet helmet. The French term for the same was camail. These were attached to the helmet using vervelles.
The aventail was a popular defence during the early medieval period and was replaced by integral coifs, plate gorgets and mail standards.