The tension wrench is the most important tool in lock picking and the one most kits get wrong. It applies the light rotational pressure that makes pins bind — tension is 80 % of the skill. Here are proper wrenches in every style: L-shaped, top-of-keyway, twist-flex and adjustable.
Guide
Tension Wrenches
A pin tumbler lock only opens when every pin is at the shear line at once — impossible to hit by chance. The tension wrench applies a tiny turning force to the plug so that, because of manufacturing tolerances, one pin binds at a time. You set that pin, the plug turns a fraction, the next pin binds. Without tension, nothing binds and nothing you do with the pick matters. That is why the wrench, not the pick, decides whether you succeed.
The classic L-shaped wrench that sits in the bottom of the keyway. Simple, fits most locks, included in every set. Comes in several widths — a wrench that rattles in the keyway gives poor feedback.
A flat bar that sits at the top of the keyway, leaving the whole bottom free for the pick. Preferred by most experienced pickers for single pin picking and for spool pins, because the feedback is clearer. Comes in 0.040" and 0.050" thicknesses to fit European keyways.
A wrench with a twisted section that acts as a spring, smoothing out your hand and making it much harder to over-tension. The best beginner wrench — one is included in all our beginner sets.
Tools that clamp into the keyway or use a spring dial to give constant tension. Useful for disc detainers and for pickers with hand fatigue.
Less than you think. The weight of a finger resting on the wrench. Beginners use five times too much, which over-sets pins and makes spools lock up. If a lock feels impossible, halve the tension before changing anything else. Our guide's first exercise is picking a clear lock with the wrench only touched by a fingertip.
Because keyways vary. A wrench that fits a padlock may be too thick for a Euro cylinder and too thin for a wafer lock. A small assortment of BOK widths plus a pair of TOK bars covers everything in our practice locks range. Tension wrenches are also the tool you lose or bend most often.
All the tools here are legal for hobby use in nearly all of Europe (legality by country). Learn to use them in how to pick a lock for beginners.
