Smooth the carpet runner up the riser from the tackless strip that is fastened across the bottom of the top riser. Risers are the vertical boards at the back of stair treads that lead to the next higher tread. Treads are the horizontal part of the stairs for foot traffic.
Push the runner against the underside of the hardwood floor nose or trim at the top of the staircase.
Cut the carpet straight across along the underside of the trim with carpet shears or a utility knife. Cut slowly and with a firm hand to prevent crooked lines and pulled yarns.
Apply carpet fray-stop liquid across the cut edge of the carpet runner, and let it dry as long as the manufacturer recommends.
Press the top edge of the carpet runner against the top of the riser. Staple the top edge of the runner to the riser, just beneath the hardwood flooring nose or trim, with a staple gun and 9/16 staples. Space staples approximately 3 inches apart.