maybe this will help... cross section of the tank rim with cover. Extend around all four sides of tank (the lt brown/orange colored piece stayed on the tank at all times, the dk brown+screen came off). The wood I got pre-made at my local Ace hardware, as well as the screen mesh.
The clips I had were quite sturdy, and I made sure by lifting up at various points of my top that it wasn't liftable at any point by me (so tehrefore wouldn't be push-up-able by a 3-foot cornsnake). I used four clips. I also had a 2x8 board across the top of the tank, but mostly to keep my cat from breaking the screen when she sat on top than to secure the lid in any way.
how do get into the cage?