Cutting stepped tenons - step three , width jig

This is the only step that involves a measurement. Measure and cut, with square ends, a piece that will fit in the rebate, to the exact width of the finished sash.

Screw this into the rebate (screw only need to just grab). Cut off the excess timber but leave a bit (less than the thickness of the MDF) for trimming on final assembly.

Use the same piece for a jig on all the horizontal sash rails, I marked an L & R on the jig and rail as the jig will need refitting on the same screw holes.