bag in which to wrap the body for a particularly intense form of bondage, custom-made from leather or rubber or improvised from a sleeping bag and rope or straps.

Sleepsacks are a popular type of bondage (BDSM) gear. Sleepsacks are primarily used to confine a person comfortably for an extended period of time. http://www.informedconsent.co.uk/encyclopervia/Sleep_sack Similar to a conventional sleeping bag, a person climbs into a sleepsack and is usually zipped into it up to their neck. Generally sleepsacks are very tight on the body, adding to the bondage aspect of the experience.