Cut the panel

Saw the panel to width first. It should be exactly as wide as the rails are long. Use one of the rails to position your saw’s fence

then cut the panel

(Photo 8), (Photo 9).

To figure out the panel’s length, assemble three sides of your door

Measure the distance between the tenons and subtract 1/16 in. Set your saw’s fence to this dimension, then saw the panel

Sand all edges of the panel so it slips into the grooves easily.

(Photo 10). (Photo 11).