I keep coming across pick retailers selling Letter Box-Type Tension Tools
Lever-Type Letter Box Lock Tension Tool x4 (scroll to near bottom of the page)
Letter Box Tension Tools for Letter Box Locks
Tension Tool for Letter Box Locks (3/4")
All I've managed to understand so far is that these tools are for tensioning a lever-type lock known as a letter box type lock. I don't believe we're talking about letter box locks, but a type of lever lock.
The thing that's bugging me is that I've never heard of them, and I'd love to understand why these tools are so widely sold, but above all, how they are used.
I found this, but I still don't get it: http://www.lockpicking101.com/viewtopic.php?f=8&t=12578
Any help much appreciated.
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