In Fig. 22 is shown an enclosed stairway, illustrating the method of laying out the wall stringer, easement curves, etc. The widths of the winding treads at the wall are projected down from the plan by lines k I, m n, etc. Then the wall stringer a b, at right angles to the main wall stringer a e, is revolved as shown, parallel to the main wall stringer and laid out in a similar manner; a' b' c' d' shows the stringer a b in elevation. The stringer e f is treated in a similar manner. The story rod is shown at the left, and the steps are projected from it and from the plan, as shown at step 4. Where the treads are wide, as in steps 1, 2, and 3, the line of the nosings makes an angle with the horizontal different from that made by the line of the nosings in the body of the stairway. This is because the uprights, or risers, remain the same, while the horizontals, or treads, vary in width.