A cage made of plastic, silicone,
metal, or another material that fully encompasses a penis. The cage is then locked so it can't be taken off without the key. It's designed to prevent erections &
masturbation and is often used in bdsm relationships where the key is given to someone's significant other, called a keyholder. It is still possible to masturbate in them however, either by using a vibrator on the cage or using a
dildo in the ass.