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
JACK… FOR NUTS
The so-called unusual mechanism established at the Irkutsk industrial College for tightening heavily loaded threaded connections of large diameter. Anyone who has had to screw up the nut...
IS-3: THE LAST BREAKTHROUGH TANK
Drafting of a new heavy tank, much superior to commercially produced is-2 on armor protection began in accordance with the decree of GKO No. 5583 on 8 April 1944 and had its prehistory. A...