After publishing the Kerfmaker, Thing:1345031 I had a number of requests for the Tenonmaker so I modified the design and have tested this out. It works well and even had the flip down part that prints as one piece. The top part will need supports.

printed at 30% infill and 3 exterior walls and used PLA to avoid the warping since the ends needed to be very square.

Hardware needed: 2qty. M4x20mm hex cap bolts Lowes 2qty. M4 nuts. Lowes

And here is a video turorial https://www.youtube.com/watch?v=Cs9Ychd--qk

Added the 123D Design files too incase anyone wants to monkey with the design. Just be sure to "remix" it from mine.