Since I choose to use black foam board - I applied it with black Gorilla Tape (it's kinda like Duct Tape, but IMO a heck of a lot stronger) Gorilla can be picked up at most hardware stores and also Wal-Mart (I think).
All my tanks are display tanks - so this method gave me the cleanest look, and everyone that visits always compliments the appearance of my tanks (even though they may be scared of what's in them...lmao).