A suspension bar is a bondage device designed to facilitate suspension bondage. It consists of a steel bar with one or more primary attachment points to attach it to the hoist cable (or overhead fixing point) and a number of secondary attachment points to attach chains or rope. Suspension bars have a passing similarity to spreader bars and can be used as such. However, spreader bars should never be used for suspension bondage, as the loads placed on them will almost certainly cause them to break.
Most suspension bars employ two short chains attached at either end of the bar and joined together at the attachment point for the hoist. This increases the stability of the bar (preventing it see-sawing) but it does increase significantly the height of the hoist required in order to use the bar. If ceiling height is an issue then it should be possible to remove the chains (although check with the manufacturer first) and the winch cable attached directly to the middle of the bar.
Suspension bars vary in width; the type of bar needed will depend on the sort of bondage you want to do. Short bars are generally used with suspension harnesses, medium bars for spreading the feet and hands, and long bars for horizontal suspension bondage.
Issues in using suspension bars
A great deal of bondage imagery shows captives being suspended from their wrists. For BDSM play, this form of bondage does not work very well; even if you are using suspension cuffs the strain on the captive's shoulders will quickly become very uncomfortable (in a very unsexy way) and they will need to be let down. Suspension bars (together with a hoist) are great for rope bondage; the multiple attachments points allow the rigger to spread the load of the captive's weight much more easily and provides interesting new ways of tying the captive.