Im bored and happy to write this so here goes so any one reading this bare with me.
When locks have security pins in them it makes the plug go clockwise or whatever direction your tensioning it the plug will go a bit more degress and look like its about to open but it wont.
lets say this is a 5 pin tumbler and the spools are in 2 and 4.
If you false set number 2 when you pin pick that pin (push it up) it will make the plug rotate backwards. This is called negactive pin rotation when you push this pin up it will either reset that pin or set it.
Iv'e did this on my Yale 6 pin (2 spools) and its a piece of cake now. - Jason thx for reading
