This is a tray that sits on the top edge of a wall-mounted whiteboard in order to hold markers.The included .stl is a tray 100 mm long meant for an IKEA KLUDD whiteboard (http://www.ikea.com/us/en/catalog/products/10114874/).If you're using an IKEA KLUDD whiteboard, four copies of the included .stl will reach most of the way across the short edge of the board.If you're using another whiteboard or have a printer that can handle objects taller than 100 mm, edit the included .scad file.