Even after you assemble one, this classic toy, with blocks that appear to flip down the sides, still seems mysterious. The secret is in the pattern of hinges made by the ribbons.
Measure, mark, and cut the two basswood planks into 4-inch-long sections. You should end up with 12 blocks.
Coat the top of the first block with tacky glue. Place the ends of the three ribbons as shown, then add a bit of glue on top of each. Stack a second block on top to form a sandwich.
Lay the ribbons across the sandwich as shown.
Place the next block on top of the ribbons. While holding the block in place, gently tug the ribbons so that they're straight and snug but not tight. Cover the block with glue, lay the ribbons over the top, then add more glue to the ribbon pieces. Top with another block to complete the second sandwich.
Repeat steps three and four to make four more sandwiches, trimming the ribbons to fit inside the last one. Place the stacked-up toy under a heavy book until the glue dries. To start the blocks cascading, hold the top block and tilt it forward and back, as shown.