A bondage wheel is one of the largest (and most expensive) pieces of SM equipment found in a BDSM dungeon (BDSM). It consists of a large vertically mounted rotating wheel to which the bondage subject is strapped. In this respect it is similar to a Saint Andrew's Cross. The difference is the bondage wheel can be rotated allowing the subject to be turned upside down. The subject can either be strapped facing the wheel (suitable for whipping) or facing out (for genital access).