A Question On My Alignment System 4 May 2018 / Paul Sellers / Paul Sellers' Blog / 10 Comments Question: Paul, I don’t understand what the alignment pieces did. Their tenons are smaller than the mortises, so they don’t register the two sides vertically relative to each other. The two sides are rigidly clamped when we put in the alignment pieces, so it doesn’t seem they can move anything into position. Would you please give some examples of problems they would catch and what you would see? Ed Answer: It’s a good question. Clamping up a table frame with two mortises to each leg is a simple enough task. You can glue the whole of eight mortise and tenons all at once pretty well. More complex frames with the added raised panels within the frame can be difficult. It’s more critical when the tenons fit without air between the walls of the mortise because of things like glue freeze, air pockets at the bottom of the mortises and then additional alignment issues that come as a result of clamping pressures. It’s not uncommon to glue up subassemblies as opposites—two end frames or a front and a back. Set them aside to dry and then do the counterparts later. Simple! Well, not necessarily. In the case of this chest it was especially difficult because the clamps are not square on to flat faces as say with a normal table or chest. The angled presentation means they are clamped on rounded corners. This in tun means that the pressure can cant the leg under the clamping pressures, causing the adjacent mortises to misalign along the long axis of the chest. Using my method means the the insides of the mortise holes enable me to use the parallel walls of the mortise hole to perfectly orient the legs and thereby the mortises so that when the subassemblies as frames dry they are ready to receive the adjacent rails and panels. The stubby temporary rails keep everything perfectly parallel because the stops in these temporary rails prevent anything but exactness. Basically what we have achieved is a risk free gluing up system for what could otherwise be a very difficult glue up. That said, I would do this with non complex glue ups too.