Two boards.
One real joint.
A short exercise for learning the manual joinery workflow. Work in a new practice project and keep your furniture project saved separately.
STEP 1
Set up a rail and leg
Choose Project → Open → Save named copy to preserve your current work, and download a project backup before starting a practice project. Sketch and extrude a 12 × 3 × ¾ in rail and a 1½ × 1½ × 12 in leg. Place the rail end against the side of the leg, with the rail’s 3 in face vertical. These are practice dimensions, not a furniture design.
STEP 2
Choose the two parts
Open Assemble → Joinery, or press J. Select the rail, then the leg. The dialog names the detected faces. Check them and use Swap if the acting and receiving parts are reversed.
STEP 3
Choose mortise & tenon
Confirm the faces, then select Mortise & tenon. The rail is the male part; the leg receives the mortise. Start from the stock-aware settings and read any validation messages before changing them.
STEP 4
Inspect both cuts
Open Preview both cuts. Use Exploded to see the tenon and mortise separately; use Section to look inside the receiver. Review the tenon dimensions, mortise depth and remaining stock. Advanced tool settings cover bit size, clearance and corner treatment.
STEP 5
Create, seat, then change the stock
Add the joint, then use the Inspector’s seating controls. Change the rail thickness from ¾ to 13/16 in and inspect the joint again. Check Issues and verify the fit; Undo returns to the previous dimensions.
Read the joint before changing it
The tenon is the tongue left on the end of the rail. The mortise is the pocket in the leg. The shoulders around the tenon meet the leg’s surface when the rail is seated. In Section, follow each surface: the tenon’s cheeks, its end, the bottom of the mortise and the wood remaining beyond the pocket. A plausible assembled outline does not show whether those hidden surfaces fit.
Explode the pair and check that the mortise belongs to the intended side of the leg. If the cut is on the wrong face, return to face selection before adjusting dimensions. Increasing clearance will not correct a wrong mating face. Keep changes small and inspect one parameter at a time so you can tell which change caused a problem.
When the rail changes thickness, inspect the shoulders and remaining leg wall again. A joint that fit the original stock may need different settings. Use the Issues panel alongside Section; neither a quiet issue list nor a smooth outside surface replaces looking at the cut.
Before taking the design to the shop
Measure your actual stock after milling. Nominal lumber sizes and the dimensions in this exercise are not a substitute for that measurement. Check the available cutter, corner treatment and intended assembly direction. Square tenon corners and a round-ended mortise need a deliberate matching treatment.
Make a test joint in scrap with the same thickness and tooling before cutting your project parts. Compare the test fit with the modeled clearance and revise deliberately. This exercise teaches the interface; it does not establish a load rating or a universal furniture joint specification.
Keep a useful practice record
Save a named practice copy and download its project file. Record what you changed and what you observed in Section. Reopen the practice file separately when you want to repeat the exercise, and return to your original furniture project through Project → Open.
Opening the app does not load a sample or replace your project.