Clamp the wood to the workbench. Use the 12mm spade bit to drill through the timber. Repeat this process for all the wood except the pieces at the end, where the rod will be inserted and secured. For these pieces, clamp them and use the 22mm spade bit to drill halfway through the pieces of wood, this creates a recess to hide the ends of the rods. Finish off the holes with the 12mm spade bit.