Computer Cases and Risers
Most computer cases are made from steel or aluminum and are capable of carrying an electrical current no matter how small. Since the motherboard attaches directly to the case, you need a way to protect the motherboard from direct contact with the case’s inside back wall.
Motherboard risers are used to lift the motherboard away from the case so that there is no chance of an electrical current reaching the board from the case. Also, risers protect the motherboard from the effects of static electricity and short circuits that could occur if any metal touches the surface of the circuit board. A motherboard is really just a large-sized circuit board with many connections running throughout its thin form.
Most motherboard risers are made from brass or plastic because these materials are poor conductors of electricity. While brass is a sturdier material and less prone to breakage, plastic is nearly a perfect insulator of electricity, making it impossible for electric current to be transferred from the case to the motherboard.
Risers come in different sizes to accommodate various applications and form factors. Expansion cards such as video and sound cards must match up to the ports in the back of the case for a perfect fit. Different sized risers allow the builder of a computer to custom fit the motherboard to the case to allow for any miscalculations made by the case or motherboard manufacturer.
Every motherboard has a specific number of holes ranging from 6 to 10 that match up to the holes on the inside wall of the computer case. You simply screw the risers into the computer case, match up the holes on the motherboard, and lay the board on top of them. Then, you use screws to secure the board to the risers and, consequently, create a nice tight connection between the board and the case.