i remember when i first had my corn snake home; he was a 60g worm and was given to me in a 20gal with no locking lid. i thought he's 60g, he's not going to push that lid up. well a week or so goes by and i've been watching how he manages to crawl along the lip of the top of the enclosure by some sort of witchcraft. one night i'm just casually watching him defy gravity and then, all of the sudden, his head is somehow poking outside of the lid. he somehow managed to wedge his stupid face underneath the lid and push it up to make his way out. i allowed him a minute or so of freedom, and safely tucked him back in and secured the lid. he now resides in an enclosure with a secure locking lid.
don't ever underestimate a snake that wants to get out!