All blocks are provided with recesses to accommodate marking tags, which snap into place. In almost all styles, provisions are provided for at least two tags.“K” style marking tags feature a large surface area, and are provided in strips of five to ten markers. Markers can be installed in strip form, or individually. Tags are available in a wide variety of pre-printed styles, including sequential numbers, individual digits or letters, symbols, and varying orientations. All blocks are provided with recesses to accommodate marking tags, which snap into place. In almost all styles, provisions are provided for at least two tags. The “K” style marking tags feature a large surface area, and are provided in strips of five to ten markers. Markers can be installed in strip form, or individually. Tags are available in a wide variety of pre-printed styles, including sequential numbers, individual digits or letters, symbols, and varying orientations.