You can put it on the outside, but definately not on the inside. The humidity caused the tape inside to droop. I wrapped the tape over and over on the outside and under, but it was when I cut a circle in the top and the bottom on each side of the screen to allow for the ceramic heat lamp that I weakened the tape. The bottom section peeled away and hung down just enough for him to get his bottom jaw stuck as well as his sides. I woke up and found him hanging there, thinking he was dead, I touched him and he moved. I then cut the tape from the top and took him to the kitchen counter where I carefully removed the tape.

Now I use a damp towel on top and leave a section open where the ceramic heat lamp is. The towel seems to dry on its own and I keep re wetting it daily. No mold has developed on it and the humidity level is about 50%.
I never thought twice about using the tape and wonder how many others have had this happen to their snakes. I hate glass terrariums because the tops are screened which does not promote good levels of humidity. I am going to buy a smaller boaphile cage for the ball pythons and a larger one for my red tail boa. I would rather spend a bit and get a handle on the proper conditions than take my chances with a cheaper set up.