Card holder for board games or Magic the gathering. It has docking lugs for stacking so that you can have a discard pile above (or below) the main deck (I have yet to print a second one to test if this works). It holds firefly board game cards in deck protectors, I've also tried it with MTG card in deck protectors as well. It is just tall enough to hold an EDH/Commander deck (100 cards) in deck protectors (although this will prevent you from stacking a second on top, Nothing to stop you putting the cards on top and having another underneath for discard though) Update: I have printed second one today (09/April/2015) and they stack just fine. Update 06/05/2015 Added picture of stacked Card Holdersno instructions per se, Just a straight print job.