How do i keep my snake cages lid down?

  i am the owner of a two year old corn snake. i was keeping him in a 20 gallon tank but it was getting too small. today i went out and bought a 33 gallon tank and it is the perfect size for him. the only problem is im having trouble getting the new lid to fit tightly on and the clips to hold it are too weak. any tips on how to keep him from escaping?
Put things such as books or small weights on the corners.

Corn snakes are insanely smart when it comes to escaping.

Best wishes.
Like the other answer said a heavy book, or rock or reinforce the clips to make them stronger. Or buy a new lid. But I think a big book would work just fine until you are ready to get a new lid.
I use bricks on the corners to hold my lids down when I use glass tanks. I have also used bungee cords in an emergency until I could buy a better top or a vivarium with sliding doors.
Put a heavy book on top of the lid.