yeah, i imagine with a little ingenuity you could prob fab a locking door pretty easily. You can buy a lock mechanism from any lock smith. Then take a hole bit and a little bit of tinkering and you have a locking door. It cant be that hard to do on your own. But seriously, if someone wants to steal your gas, do you think there is any lock or mech you could put on that little door that a crow bar couldnt solve in two seconds. I mean, you can only build a door as strong as its hindges and something tells me the fuel door hinge isnt too strong.

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