There are two linking board pilot hole jigs for accurately locating the positions of pilot holes. One each for the left and right sides of the boards. Ream the holes in the triangular pattern with a 3mm (1/8") drill bit.
Stack the linking boards so that their edges are up and mark that edge with a pencil.
Place one of the pilot hole jigs on the end of a board with the marked edge of the board on the same side as the narrow stop at the bottom of the jig. Push the board firmly into the jig and with a sharp pencil, mark the location of the pilot holes. Repeat with the other jig on the opposite end of the board ensuring that the marked edge is towards the bottom of the jig.
Repeat with the remaining linking boards.
Drill 2mm (1/16") pilot holes at the marked positions on each board being careful to not drill all the way through the board.
Vertical Board Through Holes
Locate the vertical board through hole template and ream the holes with a 3mm drill bit.
Butt the template against one corner of a board as shown in the picture and mark the locations with a sharp pencil. Repeat on the opposite end of the board. Mark all three vertical boards.