How To Make A Pitch Block
The pitch block is a right triangle cut from 2 x 12 lumber that will become a critical measuring tool for constructing the balustrade. Save one of the triangles cut from a stringer. (Remember that critical measurement and cutting of stringers is a basic necessity for a good stairway. Accuracy to within 1 /32" will make the installation go smoother.)
Save a triangle of wood from your stringer. Mark it as shown. It will become your pitch block.
The pitch block reproduces the exact angles of the stairway. Mark its three sides as shown in Fig. S-3a, and put it aside for later use.
If no triangle cut from a stringer is available, lay a straightedge across the tread nosings and use it to mark a piece of plywood as shown in Fig. S-3b. Make sure the plywood is square and that it is held firmly against the tread nosing.
Making a pitch block for an existing stairway
NOTE:The rise and run should remain the same throughout the stairway; however, IF THE RISE AND RUN VARIES FROM FLIGHT TO FLIGHT, make a separate pitch block for each flight of stairs.