Cut along the edge of the carpet to gain a handhold, using a razor knife. Grasp the carpet and pull it free from the tack strips below. Pull any stubborn sections with your pliers to free them from their position. Cut the carpet in small sections and discard the scraps in a heavy-duty trash bag.
Place the tip of your nail puller against the seam between the tack strips and the subfloor. Tap the back of the nail puller with your hammer to knock the tip of the puller under the tack strips. Pull the upper handle of the nail puller to loosen the tack strips. Grasp the strips with your hand and pull them free. Dispose of the tack strips in your trash bag.
Pull up carpet padding still stuck to the stairs by hand. Scrape up any debris or adhesive stuck to the subfloor with your 5-in-1 putty knife. Sweep the stairs from top to bottom to remove any loose dirt, dust or debris with a broom.
Measure the height and width of the vertical face in front of the top step with your tape measure. Transfer your measurements to a 1-by-12-inch board. Mark the width of the step along the length of the board. Draw a pencil line across the width of the board, using your square as a straight edge. Cut along this line with your circular saw.
Measure the width of the board to match the height of the step. Make your mark with the pencil and speed square. Cut along the line to complete the fabrication of the piece. Place the board into place and secure it to the subfloor by driving a 6d finishing nail every 4 inches with the hammer. Countersink the heads of the nails with your nail set.
Measure, cut and attach the horizontal tread board of the top step. Continue your way down the stairs. placing the vertical board of each step before the tread. Countersink the nail heads as you go.
Press wood putty into the top of every nail in the stairs. Apply a bead of caulk to every seam between the boards of the stairs as well as the border between stairs and walls. Coat the stairs from top to bottom with wood stain, using a paintbrush, and allow the chemical to dry completely.
Brush on a thick coat of polyurethane, starting at the top of the stairs and working your way to the bottom. Allow the polyurethane to dry before using the stairs.