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What are you housing? If it is a snake, then it is best to simply leave the lid intact, and drill holes in the side. This gives you more control over the environment inside (one of the main reasons rubbermaids make great cages), and permits heating from below, which is the most efficient way of heating most snakes.
To answer your question...
Assuming you have purchased hardware cloth, it can be cut with a good pair of household scissors or metal cutters. It can be securely fastened to the top by using screws and bolts.