Build an arch strong enough to support your weight without glue with this working model! Teach basic concepts of equilibrium, force as vector, and arch structures. Use stand alone or in conjunction with our Catenary Arch (47701-00 ). Includes: 23 precision-cut hardwood blocks (average size 2.5 cm x 7.5 cm) in 6 shapes, predrilled buttress in 3 sections, hardware, instructions and full-scale template. Recommended for grades 6-12.