Okay, you've assembled your two cubes and painted them black. Read part one if you don't know what I'm talking about. The next step is to add a door. I can't tell you the appropriate size because it will depend upon how thick the walls of your cubes are. Measure the height and width of the open side of your altar. Be sure to measure in a couple of locations because the cubes may not be perfect. Remember the carpenter's motto: measure twice, cut once. Your local lumber yard can cut a board to size for you. I suggest using plywood at least 3/8" thick. If you go much thinner the door may warp. The choice of hinges is up to you. You might prefer "invisible" hinges (they're completely on the