with 180- or 220-grit sandpaper, and paint the blocks contrasting colors. If you're using fine-grained hardwood blocks, leave them unpainted or finish with varnish or oil before attaching the tapes. 3 Stand the blocks on end and, using a sharp pencil, mark a centerline for one tape that will go over, under, over, under all the blocks. Turn the blocks over and draw the same centering line on the opposite end. 4 Place the first block on a table. Attach a length of binding tape (available from any sewing shop) to one end of the block with two brads. The tape should be centered over the centerline. Then tack the two side tapes to the opposite end of the first block; set in each side tape 1/16 in. from the block's edges. Lay the tapes across the face of the block so the two side tapes go in the opposite direction to the center tape, as shown in the top drawing at right. 5 Place a second block on top of the first and wrap the tapes around the block (see the second drawing at right). Pull the tapes snug, but not too tight, making sure no tape is twisted. (If the tapes are too tight, the blocks won't flow when you operate the toy.) Tip the block on end and nail each tape with two brads. 6 Continue adding blocks and attaching apes with two brads to the alternating ends of each block until you reach the top of