How to Make a Stair Tread Gauge

Measure the width of several stair treads with a tape measure. Calculate the average width of the treads. Subtract 2 inches from the average width. The result equals the overall width of your stair tread gauge. Draw a tape measure across the 3/4 inch thick scrap wood and mark the overall length of the gauge on the wood's face.

Align a carpenter's square with the width mark and run a pencil along the square's edge to create a straight, perpendicular cut line across the wood's face. Cut the wood to size with a circular saw.

Lay out two identical, scalene triangles on the scrap lumber with the tape measure, pencil and carpenter's square. Scalene triangles have three different sides and three different angles. Make one side of the triangle equivalent to the depth of treads and ensure that none of the triangle's corners form a 90-degree angle. The tread-length side will butt against the wall. Leaving out 90-degree angles allows the triangles to fit into poorly-squared corners.

Cut the triangles along the lines with a circular saw. Select a wood bit slightly larger than the diameter of the bolts' shanks. Mount the wood bit to the power drill. Bore a hole through the center of each triangle. Align the sides of the triangles that equal the tread depth with the ends of the board that form the gauge's body. Press a pencil through the triangles' holes and transcribe a bolt hole marks onto the face of the board.

Clamp the board to a stable surface, such as a work bench or sawhorse. Align a plunge router's bit with a bolt hole mark. Plunge the bit into the board's face and route a channel toward the board's end, roughly 3 inches long. Route an identical channel at the opposite bolt mark.

Use a countersink bit equivalent to the size of the bolts' heads. Mount the bit to the power drill. Use the countersink bit to enlarge the bolt holes on the triangles' bottom faces; the bottom faces are the sides of the triangles that do not press against the board that forms the gauge's body.

Align the triangles' bolt holes with the board's channels. Position the countersunk side of the holes to face away from the board. Slide bolts through the triangles' bolt holes and into the channels. Snug the bolts' heads into the countersunk holes. Thread wing nuts onto the bolts' shanks until the wing nuts sit flush against the board's face.

Place the assembled gauge on an unfinished tread. Loosen the nuts and slide the triangles to the tread's sides. Align the triangles with adjoining walls or skirting and tighten the nuts to create a template for the stair tread.