backplate

noun

1. 1.A plate protecting a fighting person's back.
2. 2.(underwater diving) A plate harnessed to a diver's back, to which the gas cylinders are attached.
3. 3.A metal plate on the rear of a computer's casing, used to cover a port or slot.
4. 4.A wood or metal plate that serves as a backing for an object.
5. 5.A rigid metal plate inside the brake drum, which supports the wheel cylinder, brake shoes, and other parts of a drum brake.