How to Lay Stairs With a Steel Square

Obtain the measurements required for your step rise (the height of each step on the stairs) and the step run (the depth of the tread, which is the step surface. Calculate the dimensions by hand, use an online calculator or read the specifications in the building plans.

Lay a large steel carpenter's square flat on your work surface. Consider the direction the angle formed by the intersection of the square's legs makes. Point it either toward or away from you -- whichever feels most comfortable.

Locate the rise measurement along the ruler reading on one side of the square. Again, it doesn't matter which side of the square you read. The square flips over so you can start with either, and the completed stringer will flip end for end as well, allowing you to put the rise first.

Align a short piece of tape -- transparent, masking or duct, the type isn't important -- with the precise rise measurement. Find the run measurement on the opposite leg of the square and repeat. Both the rise and run are now marked by tape.

Hold a 2-by-4-inch board or similar straightedge up to the measurement markings, with the edge aligned precisely. Clamp the straightedge in place to secure. Use stair gauges alternatively, tightening to attach.

Place the square at either end of the stair stringer -- generally either a 2-by-10-inch or 2-by-12-inch board. Turn the square so the point is away from you with the rise or run at the beginning of the board. The edge of the straightedge will rest, and ultimately glide, along the edge of the stringer. The portion laying over the top of the stringer, from straightedge to point, is the exact outline of the step desired.

Outline the step with a pencil, up one side of the square and back down the other, creating an upside-down V. Slide the jig down until the beginning edge of the square rests at the ending point of the V. Mark the jig outline again. Continue down the length of the square until complete. A zigzag design results.

Cut the finished product out, using a power saw until you are close to the inside point of each step and switching to a hand saw for precision. Cutting into the wood past the depth needed weakens it considerably. Use the finished stringer as the template for additional stringers as needed.