In BDSM, a cage is an enclosure, usually made of metal bars, sometimes also of wood, used to confine a submissive. In dungeons, cages are standard equipment; however, cages are also placed in residential basements or spare rooms.
Cages are used as a means to restrict the freedom of the enclosed person in an obvious way. They have a connotation both of animal husbandry and of prisons.
Cages are relatively weighty and costly, and are therefore found less frequently in the non-professional sub-culture, even though they are highly appealing to many sadomasochists.
Cages come in the following variants:
Most cages are built in rectangular box shape, but they are also built in various other forms, e.g., as a pyramid, dome, or sphere.
Cages can be built in various sizes, reaching from the size of a coffin to a cage that holds several persons. Very small cages do not only prevent a breakout, but they can also restrict the enclosed person's movements, who then can — depending on its design — only stand, lie, or squat.