Since we were on kind of a kick of cutting things in half, we chopped up this old Ford Dana 44 caliper. You can see about half of the piston and the seals that help it do its job. Also visible are the holes in the back of the caliper for the bleeder screw and where the brake fluid enters the caliper. As the fluid is forced into the caliper the piston moves out. One brake pad rides with its back to the piston while the other pad has its backing plate to the opposite side of the caliper. The rotor is sandwiched between the pads and clamping force slows the turning of the rotor and wheel.