I've run into a concerning roadblock: I don't know what wood the bookshelf is made of. And there aren't too many ways to find out, as the furniture itself is probably older than I am.

Will completely sealing the inside with tile be enough to protect the snakes IF the shelves are made of pine? (I sort of doubt that it is pine, it feels too hard to be pine, but I'll do what I can to find out.)