IgnoreMe
5,000+ posts
CarAudio.com VIP
they mean corners as in the 90 degree angle that is formed when 2 pieces of mdf are put together. they mean to cut a long triangular piece and put that into the corner. imagine this /\ is the 90 degree angle in the box (lol i know its not really 90 degree but whatever) and now imagine sticking a triangle in there. now that corner is not really a true corner anymore. its actually round looking almost.