grid of equilateral triangles (each measuring .28"). It is invaluable for any kind of three dimensional design including architecture, landscaping or sculpture. Some artists enjoy using it to draw puzzles or complex or labyrinthine 3D images with boxes and staircases (rather like the style of MC Escher). It has become particularly popular for planning 3D Printer projects. Some schools and many colleges now offer 3D printing facilities and classes. It may also be used for geometry.