To determine the length of a roof ridge using a steel square, you would first mark a point on one end of the ridge. Then, place the steel square with one leg against the marked point and align the other leg with the ridge. Keeping the square firmly against the ridge, walk along the length of the ridge while constantly checking that the square is aligned. Once you reach the other end of the ridge, mark the point where the square aligns with the ridge. The distance between the two marked points will give you the length of the roof ridge.
