Leather sleepsacks are generally very confining but do not stretch. If they are sized correctly they are very comfortable for long-term usage, and many bondage enthusiasts spend entire nights comfortably confined in them. In order to make the tightest fit possible, many leather sleepsacks have small D-rings down each side of the main zipper along the front of the sack, which allows the sack to be pulled tighter around the body using rope laced between the D-rings. This system of D-rings and rope lacing also protects the zipper from any stress that the occupant of the sack might exert on it. To further add to the confining aspects of the sleepsack, there are usually straps or belts that go around the body at intervals along the length of the sack, starting at the collar and going down to the ankles. To keep the straps in place and prevent them from shifting, they pass through larger D-rings down the sides of the sleepsack.