The term "bondage" describes the practice of physical restraint. Bondage is usually, but not always, a sexual practice. While bondage is a very popular variation within the larger field of BDSM, it is nevertheless sometimes differentiated from the rest of this field. A 2015 study of over 1,000 Canadians showed that about half of all men held fantasies of bondage, and almost half of all women did as well. Strictly speaking, bondage means binding the partner by tying their appendages together; for example, by the use of handcuffs or ropes, or by lashing their arms to an object. Bondage can also be achieved by spreading the appendages and fastening them with chains or ropes to a St. Andrew's cross or spreader bars.