Chastity cages, cagers, or harnesses (sometimes accompanied with belts that can be tied around the waist) are often used as a type of submission tool in BDSM play, for teasing, or for sexual arousal purposes.
Usually, you’ll find penis cages (also called cock cages) that envelop the penis with a kind of tube, which typically holds the penis at a downward angle and makes an erection and ejaculation difficult or impossible. As such the device can give free play to manipulating the testicles.
Typically, the cage is attached with a ring around the base of the penis behind the scrotum. Depending on the device, it may also come with a scrotum cage, also called testicle cage. Alternatively, you also find cages that only constrict the scrotum and hence deny access to the testicles.
There are different designs on the market, of which some have a hole at the tip, others vibrate or can be locked with a key, and so on. They can be made from stainless steel, leather, plastic, and silicone, among some other materials.