The trick is when you build the box you inset the sides like an 8th of an inch, wrap it like a tube and wrap it over the ends then the sides you stick a piece in there use a tool like a flat head screwdriver and get the fabric in tha corners and trim it up and never use staples it looks like crap use 3m super 99 spray glue its the best stuff that you do it yourselfers can get.