by AlexMHH » 24 Sep 2008 0:54
Just to clarify above comments, there is a very large difference between the multiple shear lines in a normal lock, and the two independent shear lines in a Small Format Interchangeable Core lock. In the case of the former, any particular shear line created between the two, or in the case of a master keyed system, three or more pins in each cylinder will open the lock. In the case of a SFIC lock, it will only open if all pins are aligned to one shear line or the other (an inner, operating shear line, or the outer, control shear line), lest the pins become caught.
In conventional locks, there is really only one shear line between the plug and body, with multiple breaks in a master keyed pin stack for this line to be created. The SFIC locks have two shear lines between the plug and body of the lock, and when the gap between top and bottom pins is aligned with one, it is blocking the other. It is very difficult to pick to only one shear line without a special tension wrench, making SFIC locks substantially more resistant to normal picking.
