Get familar with this doc:
http://www.lockpickshop.com/Lockpicking ... cking1.htm
It is the MIT Guide to Lockpicking and a common starting point for beginner concepts.
Torque wrenches are small 'L' shaped pieces of metal where the short end is inserted into the bottom of the keyway so as to give yourself ample room to work the pins with the pick. The long end is turned to rotate the plug of the lock as if the key was going to turn it.
The size you need is directly related to the size of the keyway. It must be small enough not get in your pick's way... and it must big enough be able to turn the plug.
MANY topics here discuss tension wrenches and their use in depth and offer MANY around-the-house sources for you to consider for obtaining and making them.
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