"Chaps are also popular in fetish fashion and the leather subculture, where they often are tightly fitted and worn without jeans or other garments layered beneath them other than a codpiece. They can be made of leather, patent leather, or vinyl and are worn for decoration serving no protective purpose. Worn in this manner, they are colloquially referred to as "assless" chaps."
http://en.wikipedia.org/wiki/Assless_chaps