Tension Wrench - Double-ended

Tension Wrench - Double-ended

If you're wondering what it is exactly  a tension wrench does here's a bit of insight from the folks at Wikipedia:
The Tension wrench, or torsion wrench as it is more accurately described, is used to apply torque to the lock plug to keep pins from being pushed back down by springs after they are correctly set at the shear line. A tension wrench is a tool used in picking locks. Typically shaped like a letter "L" (although the vertical part of the letter is much elongated in comparison to the horizontal part), it is used to apply tension to the inner cylinder of a lock, in order to hold any picked pins in place, while the other pins are shifted. The tension wrench is then used to turn the inner cylinder and open the lock. Despite its popular name, the tool provides torsion, not tension.