Picking a dial lock, more accurately called “manipulation,” means figuring out the combination by feel and sound rather than brute force. Unlike pin tumbler locks that use picks and tension wrenches, dial locks require patience, a quiet environment, and an understanding of what’s happening inside the lock body. The process can take anywhere from minutes on a cheap padlock to hours on a quality safe lock, and some higher-security models are specifically designed to resist it entirely.
What’s Inside a Dial Lock
Every dial combination lock uses a set of internal wheels called a wheel pack. The number of wheels matches the number of digits in the combination: a three-number combo means three wheels stacked on a spindle behind the dial. Each wheel has a notch cut into its edge. When you dial the correct combination, all those notches line up to form a single gap.
Sitting on top of the wheels is a small metal bar called the fence. The fence rests on the smooth outer edges of the wheels and physically blocks the bolt from sliding open. When the notches align, the fence drops into that gap under its own weight, clearing the path for the bolt. That’s the satisfying click you feel when a correct combination lands.
The dial connects to a drive cam, which has a small pin on it. As you spin the dial, this drive pin eventually catches a tab (called a fly) on the adjacent wheel, dragging it along. This is why you turn the dial multiple times in one direction before reversing: each full rotation picks up one more wheel. Turning right three times engages all three wheels. Reversing direction lets you set each wheel independently, one at a time, parking each notch in the correct position.
How Manipulation Works
The core technique exploits the fact that the drive cam also has a notch, and the fence’s nose passes over it once per rotation. When the nose hits the sloped edge of this notch, it produces a subtle click. This is your starting point.
To find it, turn the dial slowly to the left while applying very light pressure on the shackle or bolt handle. Listen and feel for a faint click as the fence contacts the drive cam’s notch. By noting where on the dial this click starts and stops, you identify the “contact area,” a narrow range of numbers that tells you the drive cam’s orientation. This is the foundation for everything that follows.
Once you know the contact area, the next step is graphing. For each number on the dial, you park the first wheel at that position, then slowly rotate the dial back and forth across the contact area while pressing lightly on the shackle. You’re feeling for how wide or narrow the contact area is at each position. When a wheel’s notch is lined up under the fence, the contact area will feel slightly different: the click zone narrows or shifts. Plot these readings on paper (number on the x-axis, contact area width on the y-axis) and the combination digits show up as dips in the graph.
This process is repeated for each wheel. On a three-wheel lock, you’ll generate three graphs. The numbers where the contact area narrows are your combination candidates. Because most locks have some tolerance, you may end up with two or three candidates per wheel rather than one exact number, which means trying a handful of possible combinations rather than all 64,000 (on a typical 40-number, three-wheel lock).
Why Some Locks Resist Manipulation
Lock manufacturers know about manipulation and design countermeasures into higher-security models. Underwriters Laboratories rates combination locks under their UL 768 standard. Group 2 locks are standard commercial models with no specific manipulation resistance. Group 2M locks add some design features to slow down manipulation. Group 1 and Group 1R locks are required to resist 20 working hours of expert manipulation, using advanced internal geometry that makes the contact area readings unreliable or indistinguishable.
Common countermeasures include false notches cut into the wheels (so you get dozens of misleading dips on your graph), tighter tolerances that reduce the tactile feedback, and serrated drive cams that produce multiple clicks per rotation instead of one clean contact point. If you’re working on a safe with a Group 1 lock, manipulation alone is unlikely to succeed without specialized equipment.
Tools for the Job
Basic manipulation requires almost nothing: your hands, your ears, and graph paper. A stethoscope helps amplify the clicks on safe locks with heavier doors. Some people tape the stethoscope’s chest piece directly to the lock face near the dial for consistent contact.
For more serious work, auto-dialers exist. These are motorized devices that clamp onto the dial and systematically try combinations while measuring feedback through sensors. They’re used by professional locksmiths and security researchers, not casual hobbyists. Open-source designs are available online, but building one requires familiarity with electronics and machining.
Shimming: A Different Bypass Entirely
On cheaper dial padlocks, manipulation isn’t always necessary because shimming can bypass the lock faster. A shim is a thin, curved piece of metal (often cut from an aluminum can) that slides between the shackle and the lock body. The shim pushes aside the internal latch that holds the shackle in place, releasing it without ever touching the combination mechanism.
The shim needs to reach the locking latch inside the shackle cutout. Locks with loose manufacturing tolerances leave enough space for a thin shim to slide in. You insert it along the shackle on the side where the latch engages, then rotate it inward while pulling up on the shackle. On a basic lock, this takes about 10 seconds.
Many modern padlocks now include anti-shim features. Master Lock’s BlockGuard design, for example, uses a latch with a flat profile that doesn’t overhang the shackle, giving the shim nothing to push against. The latch also has a grooved top that traps the shim tool, actually tightening its grip on the shackle when someone tries to bypass it.
Directional Dial Locks
Some newer padlocks, like the Master Lock Speed Dial, replace numbered combinations with directional sequences (up, down, left, right). These work on a completely different principle. Instead of a wheel pack, they use perpendicular internal rotors. Pushing the dial in one direction moves not only that rotor but also the two rotors oriented at 90 degrees to it. Only the rotor directly opposite stays still. The correct sequence of directional inputs aligns all the rotors to release the shackle.
These locks can’t be manipulated using the contact-area method because there’s no drive cam or fence. They’re generally resistant to traditional shimming as well, though their security level varies by model.
Legal Considerations
In most U.S. states, possessing lock manipulation tools is legal as long as your intent is legitimate, such as opening your own lock or practicing as a hobby. The legal line is intent: owning a stethoscope and graph paper is obviously fine, but using them to open someone else’s safe is burglary. A few states are stricter. California treats possession of burglar’s tools, including lock picks, as a misdemeanor unless you can demonstrate lawful intent. Virginia prohibits unauthorized possession of tools meant for lock manipulation outside of law enforcement. State laws vary enough that it’s worth checking your local statutes before purchasing dedicated locksmithing tools.
Lock sport communities, where hobbyists practice manipulation and picking on their own locks, operate openly in most jurisdictions. The general legal principle across the country is simple: pick your own locks, not anyone else’s.