This intriguing demo will challenge your students and help them visualize three-dimensional objects. One three-dimensional peg fits in three different-shaped holes, depending on which way you turn the peg. It could fit in either a circular, x-shaped, or square hole cut out in the board. It's not as easy as it looks! Concepts covered are appropriate for geometry, drafting, and physics classes. Designed by Maine physics teacher Robert Thomas. Includes: puzzle and full instructions.