You need to apply a small amount of clean DOT-3 brake fluid to the piston, piston seal, and piston bore, install the square-cut piston seal in the
Brake Caliper bore groove, ensure that the square-cut piston seal is not twisted, install the boot over the end of the piston so that the fold will face toward the brake caliper housing piston bore opening, position the piston to the brake caliper bore and seat the boot into the brake caliper bore groove and a piece of wood across the piston to be installed, apply equal pressure by hand while pushing down, install the piston in the bore, remove the piece of wood and install the bleeder valve in the brake caliper housing, the bleeder valve cap, and the brake caliper.