Yardstick, metal or wooden. Find a short length of wood, and hold the block of wood at 90 degrees to the yardstick. Get the edge at the 1-3/4 inch mark. Bolt the block of wood to the yardstick. You have a HOOK ruler now. So, hook the pipe of your draw board. Now, drill through the yardstick and attach the yardstick to the backbone of your draw board.
The wooden hook touches the pipe, exactly how your bow grip touches the pipe. That spot where the pipe and the bow grip touch, this is where you would also hook a tape measure, you always ADD 1.75-inches to this spot, where the wooden hook captures the pipe of your draw board.