If the lid is for a glass tank and is the typical black metal frame/mesh type lid you can find very strong black metal clips (2 to a package). Most pet stores carry them as well as some WalMarts and Meijers stores in their pet department. I use them on my daughters colubrid tank and even after over a year of use they are haven't stretched or warped and keep the lid very tight to the tank edge. You can use one or more sets to make sure there is no give in the lid that would allow your snake to wriggle out.