Mark the inside corners of your legs on the end grain, you can decide this by picking the faces you want to be on show. Lay your table legs flat on the bench, use a chisel hammer to make sure they are flush at one end. Use sash clamps to keep the table legs in place. Use one of the aprons as a guide, make sure it is flush with the ends of the table legs, use the square to butt this up against the apron and then use a pencil to mark across all four legs.
Remove the clamps and use the square to transfer this line onto the other inside face of the leg, these are the two face that we will cut the mortise hole in. Do this on all the table legs. Next, flush the beam of the square up to the edge of one of the table legs, use this as a guide and mark across with the pencil (this will give you a 1” (25mm) measurement from the top of the leg as the beam of the square is usually 1” (25mm) wide). Do this on both the inside faces of each table leg. Do the same from the bottom pencil mark using a ¼ ” (6mm) chisel for the guide on both inside faces.
Move the stock of the gauge down ⅜“ (10mm) but keep the distance between the pins the same. Register the stock of the gauge on the unmarked face and run it down from the 2nd pencil line all the way to the end of the leg. Mark out the waste wood with a pencil, when you reach the last pencil line, mark this part out with an ‘H’ for ‘haunch’. Repeat the same on the other marked face so the gauge is still registered against an unmarked face and repeat the process. Do this on all 4 legs.