Laying Out The Depth Of The Haunch — Joint Variation: Haunched Mortise and Tenon

On the end of your mortise piece, measure ¼” (6mm) down from the face with the mortise and mark with a pencil. Using a chisel like Paul is doing here is quick and accurate.

Note: The exact depth isn’t critical at all, since the corresponding distance on the tenon will be traced from whatever this depth comes out as.

Next, take your mortise gauge and, without altering the pins from your original setting, run it across the end grain down to the pencil line.

With your gauge still set as before, extend your gauge lines along the end grain, down to the new depth line.