Inspect the step for splinters and kinks. Smooth them away with sandpaper.
Measure the step's length (from side to side) and depth (from front to back).
Cut the stair tread to the dimensions of the step. To ensure a straight edge, hold a steel ruler along the line to be cut. Use a sharp utility knife or linoleum knife to make the incision.
Hook the tread onto the stair's nosing. The tread has a slight J-shaped lip on the front end. The nosing is the overhang at the front of the step. These should lock together.
Lay the rest of the tread down. Push it firmly toward the rear of the step.
Hammer the first nail into the front left corner, one-half inch back from the nosing and 1 inch from the wall. Do the same on the right corner, and then hammer in additional nails every 5 inches between them.
Put additional nails in the back corners. Hammer in nails every 5 inches between them. The stair mat is now ready.