Chapter 6
Basic Scrubbing
At home you can take your time picking a lock, but in the field, speed is always
essential. This chapter presents a lock picking technique called _scrubbing_
that can quickly open most locks.
The slow step in basic picking (chapter 4) is locating the pin which is binding
the most. The force diagram (Figure 5.5) developed in chapter 5 suggests a fast
way to select the correct pin to lift. Assume that all the pins could be
characterized by the same force diagram. That is, assume that they all bind at
once and that they all encounter the same friction. Now consider the effect of
running the pick over all the pins with a pressure that is great enough to
overcome the spring and friction forces but not great enough to overcome the
collision force of the key pin hitting the hill. Any pressure that is above the
flat portion of the force graph and below the top of the peak will work. As the
pick passes over a pin, the pin will rise until it hits the hull, but it will
not enter the hull. See Figure 5.3. the collision force at the sheer line resists
the pressure of the pick, so the pick rides over the pin without pressing it into
the hill. If the proper torque is being applied, the plug will rotate slightly.
As the pick leaves the pin, the key pin will fall back to its initial position,
but the driver pin will catch on the edge of the plug and stay above the sheer
line. See figure 6.1. In theory one stroke of the pick over the pins will cause
the lock to open.
In practice, at most one or two pins will set during a single stroke of the pick,
so several strokes are necessary. Basically, you use the pick to scrub back and
forth over the pins while you adjust the amount of torque on the plug. The exercises
in chapter 8 will teach you how to choose the correct torque and pressure.
You will find that the pins of a lock tend to set in a particular order. Many
factors effect this order (See chapter 9), but the primary cause is a misalignment
between the center axis of the pug and the axis on which the holes were drilled.
See figure 6.2. If the axis of the pin holes is skewed from the center line of
the plug, then the pins will set from back to front if the plug is turned one way,
and from front to back if the plug is turned one way, and from front to back if
the plug is turned the other way. Many locks have this defect.
Scrubbing is fast because you don't need to pay attention to individual pins.
You only need to find the correct torque and pressure. Figure 6.1 summarizes the
steps of picking a lock by scrubbing. The exercises will teach you how to
recognize when a pin is set and how to apply the correct forces. If a lock doesn't
open quickly, then it probably has one of the characteristics described in
chapter 9 and you will have to concentrate on individual pins.
1. Insert the pick and torque wrench. Without applying any torque pull the
pick out to get a feel for the stiffness of the lock's springs.
2. Apply a light torque. Insert the pick without touching the pins.
As you pull the pick out, apply pressure to the pins. The pressure should
be slightly larger than the minimum necessary to overcome the spring force.
3. Gradually increase the torque with each stroke of the pick until pins
begin to set.
4. Keeping the torque fixed, scrub back and fourth over the pins that have
not set. If additional pins do not set, release the torque and start over
with the torque found in the last step.
5. Once the majority of the pins have been set, increase the torque and scrub
the pins with a slightly larger pressure. This will set any pins which have
not set low due to beveled edges, etc.
