Making cheek cuts -- the part of the tenon that is parallel to the face of the board -- for tenon joinery can be a little unnerving because the wood must be kept upright and can tip into the blade, causing kickback and safety hazards, and leading to inaccurate cuts. A tenoning jig prevents tipping because the board is held securely in place so the cut is clean and accurate. Tenoning jigs can be bought from woodworking suppliers or made from scrap lumber.
Make cuts on all four sides of the board that will determine the depth of the tenon. The tenon should now be outlined with a kerf all the way around the board.
Shoulder cuts can be made either with the table saw, using a miter gauge and a fence, or with the tenoning jig. To make shoulder cuts with the jig, raise the table saw blade so that it is just slightly higher than meeting the kerf cut that outlines the tenon.
The tenoning jig rides along the table saw's fence, so the fence will need to be brought into position. Use your tape measure to determine how far the jig needs to be set from the blade so that the depth of the cut is achieved. Lock the table saw fence in place.
Place the board flush against the face of the tenoning jig and secure it in place by turning the clamp mechanism clockwise until the board is being held solidly by the jig but not so tight as to mar the surface of the wood.
Holding onto the tenoning jig's handle, make one pass through the table saw. Make certain to wear safety goggles whenever operating the table saw. While the tenoning jig makes safe, accurate cuts, be mindful of the offcut and aware that the blade can catch it and send it moving toward you.
With the saw off and the jig back on your side of the blade, loosen the clamp, turn the board around 180 degrees, clamp it in place again and make another pass through the table saw blade. Both shoulder cuts are now complete.
To make the tenon's cheek cuts, the table saw's fence will need to be adjusted to accept the new depth of cut. Use the tape measure to determine where to place the fence and lock it in place.
Secure the face of the board against the face of the jig and make a pass through the table saw.
Turn the board over so the freshly cut cheek is against the tenoning jig, secure it to the jig and make a final pass through the table saw.