During the last 25 years, I have compared various masonry pavers and setting techniques. I always felt there was a need for a "perfect" paver, so I designed my own. Dutch artist M.C. Escher's work "Reptiles" provided the inspiration for my idea of a one-piece, interlocking puzzle paver. Several design criteria, such as size, weight, strength, and ease of installation were considered. Using a template as a base, fashion a full-size model out of nonhardening modeling clay. Relief lines are detailed into the clay. Individual molds can be particularly economical for short and moderate run items. Mold choices include fiberglass, ABS, aluminum, and rubber. Each mold requires its own pallet or a mother mold if it is very flexible. For more detailed molds, choose an evaporative-type reactive release agent, which leaves an extremely thin film that forms a bond breaker with the concrete. The pavers are designed to be set on a sand bed. Properly installed dry-set CMUs are as effective as wet-set on a concrete base with mortar, but are less costly and provide greater flexibility, especially where future ground movements are expected. Proper underlayment is mandatory for a first-class job. For areas less than 200 square feet with minimal grade change, 2 inches of finely graded sand compacted with a hand-tamper is sufficient.