Used during a devil's threeway, to prevent the male's genitalia from touching during double penetration, dp. This can be cardboard, linoleum, magazines, or even a newspaper.
Bro 1: Man we should totally dp that skank
Bro 2: Aww shit, I knew I should have brought some courtesy cardboard..
Bro 1: Already ahead of you *reveals a few sheets of butchers paper*