Scott, Rockler sells quick release five star knobs in various thread pitches for about $3.50 - $3.75 each. Slide them up snug, and then tighten. Make your own corner brackets from hardwood, or plywood, with tee nuts in them. Tee nuts are very inexpensive from Reid Industries. They will sell you a bag of a hundred for about what you pay for a pack of 10 elsewhere.