The lock bolt is in the mailbox does not always withstand the encroachment of the feeder bullies. Too primitive its form is thin and the iron from which it is made.
But if you replace the stock bolt with steel plate cross-section 20×3 mm, bent as shown, so just the box, no one will open.
Recommend to read
GARDEN CART
In No. 1 of 1982 of the journal in the article "Truck changes his profession" was told about one of the most simple designs of garden carts on Bicycle wheels, with enough capacity and...
“SKYSCRAPER” CHAMPION
All conscious life Vladimir Menshikov associated with the sky. In his childhood he built flying model airplanes. Hence the choice of a profession. And as a matter of course, flying...