Sorry that I wasn't very specific about my question. I am building a 5 slot rack out of melamine. the shelf dimensions are 23 3/4" wide by 35" long. I am bought 4" THG Heat Tape, and a roll of aluminum foil tape. When reptile basics sent my order they also sent a do's and do not's list. this list was talking about the 1/8" gap that I was referring to in this post. However, they weren't very clear as to what they were talking about. Thank you, for clearing that up for me though. I appreciate it!!