For use with Pocket Tactics - for example, here: http://www.thingiverse.com/thing:41740 with thanks to dutchmogul for creating the game, and for a print and photo of the tray in use.This is an interlocking tray to keep tiles in place while playing Pocket Tactics. I recommend having four with each force, to ensure the map can grow in any direction without being too limited by the trays. Note that Pocket Tactics creator Arian Croft (dutchmogul) recommends using the non-interlocking trays, both for ease of printing, and so tiles can be placed adjacent to the trays (if desired) without the interlocking bits getting in the way.