Mechanism Kits Combination Lock Kit Make a working combination lock with a four digit combination that you set. Lesson plan available to help with the theory behind the lock mechanism Rubber Band Carpet Racer Kit Make a rubber band powered racer. The racer ejects the rubber band at the end of its travel, so the winner could be whose car or rubber band goes the farthest. Lesson plan available to help with the theory behind the racer..
