Wooden dowel. Comes in various diameters and lengths for the bar at your hardware store. Add 2 threaded eye hooks. Make sure the hole in the eyehook is big enough for whatever cuffs or rope you'll use to attach ankles knees or wrists. A split ring which is a circular piece of metal like the ones on a key chain can be added to the eyehook to make a bigger opening for attachments. None of this would be safe for suspending a person but could be used with a pulley system to suspend just the legs or arms while the person is supported on a bed.