The Strad poster contains measurements on the back, including a plate outline. This is used to create a 1/2 template for the instrument. The template is made from plastic, I used a sheet bought from a hardware store intended as a replacement for picture frame glass. This was the thinness I could find and is relatively inexpensive. This template is used to create the mold the ribs will sit on, and to set the corners once the corner blocks are attached to the mold. Placing the plastic sheet over the poster, mark back using calipers to account for the rib and overhang distance, then cut back to this line. Dividers work well for this task.