Aventails are curtains of chainmail attached to a helmet without mail covering the top of the head. The connection can be done with rings hooked into holes in the helmet or sewn onto a leather band. In this example for a 14th-century bascinet, the aventail can be taken off by pulling out the bright leather strap.
An aventail is constructed very similar to a coif with a regular amount of expansion rings added below the chin. The mail can be sewn onto a textile padding tame its movement.