Cutting exact duplicates can be difficult. If you use nails to join the pieces, there are holes to fill. With staples, it's necessary to restaple the parts as wood is sawed away.

Carbon copies won't slip apart during sawing if you use double-faced carpet tape to join them. Make your layout on the top piece of stock, then apply the tape to its back side. Remove the protective strip from the tape and firmly press the pieces together in alignment. Don't worry about tape placement between the blocks, as the saw blade won't be hindered.
—From the WOOD® magazine shop