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Test fit the newly cut riser piece to ensure it's the correct size and shape. Adjust accordingly with shears if necessary. Once satisfied with the fit, install the riser piece. First, apply a small amount of hot glue from a glue gun to the top edge of the riser piece on the backing side. Position the top edge of the riser piece flush with the top of the stair riser (underneath the stair nose of the step above). Secure this top edge with an electric staple gun, placing staples every inch or so. Next, use a carpet tucker tool to push the side edges of the riser piece firmly into the corners, concealing any exposed wood. Secure these side edges with the electric staple gun, placing three staples on each side, discreetly between the binding and the carpet pile. Finally, use the carpet tucker and hammer to press the bottom edge of the riser piece into the corner of the step below. Use the electric staple gun to place staples every inch or so along this bottom edge. Repeat for all remaining risers.