The clips for the metal screen lids were recently changed. The style was changed and they are not as easy to deal with now. They are black metal things with 2 sides. Comes in a tiny plastic package usually near the lids. You have to bend them so they fit tight under the rim of the tank and still snap over the top edge of the lid.

Pain in the butt if you ask me. My snakes are in racks but I have these lids and clips for some rodent tanks. I know petco sells them. You would be much happier with a reptile tank that has a sliding lid though.