Through Mortise & Tenon

Step 1: Measure & mark out Tenon

Step 2: Saw along markings

Fasten the tenon piece vertically and do not exceed the lines defining the height of the tenon.

Step 3: Cross-Saw to reveal Tenon Shoulders

Brace Tenon piece horizontally against a holdfast or a stop block. The waste material should fall off revealing a step, also known as shoulders, on all 4 sides of the workpiece.

Step 5: Pare Tenon shoulders

A slight hill rising towards the tenon may remain after step 4 (this happens if the chisel was not fully perpendicular). Pare this excess down and repeat on all 4 sides.

Check the flatness of a shoulder using a try-square or the length of a chisel. Ideally, the try-square or chisel should not rock from end to end of the tenon’s shoulders.

Step 6: Pare Tenon

Repeat step 5 for the Tenon. This means ensuring that the top of the tenon is square with the base (where it meets the shoulders).

Step 7: Measure and mark out Mortise

Step 8: Lay down Knife Line and start Chopping

Step 9: Clean up Mortise

Chop or pare excess material down to the drawn line on all edges until flat.

Step 10: Fitting the joint

Being able to fit the joint halfway by force of hand alone indicates a good fit. The remainder can be tapped flush with a hammer or mallet.

Otherwise, check the tenon for burnish marks, which will indicate the points of unevenness – repeat checks for flatness, pare any excess before re-attempting the fit.

Step 11: Inserting wedges

Once the joint fits well, remove the tenon piece and secure it perpendicular to the workbench.

Make a top-down cut which will divide the tenon in two, being careful not to exceed the shoulders. This creates the slot for a wedge.

Re-insert the tenon and tap a wedge of equal width into the slot using a hammer. Once tightly secured, apply some glue and allow it to dry.

The excess material from the wedge can subsequently be sawn off. If the tenon juts out from the point of exit on the mortise, simply plane it flush.