I built 2 overflows for in my tank. I had a old 20g tank that had smoked glass on the back panel. I took the tank apart and here is what I had.
http://aquahome.no-ip.com/fullsheet.jpg
I then cut up all the sizes I wanted using a glass cutter. I got the cutter from Home Depot.
http://aquahome.no-ip.com/piecescut.jpg
http://aquahome.no-ip.com/cutter.jpg
I then used silicone and tape to put them together. Pretty simple...
http://aquahome.no-ip.com/done1.jpg
http://aquahome.no-ip.com/done2.jpg
I'll let them dry, then silicone them into the tank. The smoked glass should cover up my bulkheads and my crack
Walter