Key blanks and key codes, and how keys get cut

What a key blank actually is

A key blank is an uncut key. It has the right shape, the right length and the right grooves along its sides to slide into a certain type of lock, but none of the cuts that make it open one particular lock. Think of it as a blank sheet of paper that already has the margins drawn in. The cuts are the writing that follows.

Blanks are not interchangeable. A blank made for one brand of cylinder will not even enter a different brand, because the grooves along the blade, called the keyway, are shaped to fit only certain locks. The shoulder, the part that stops the key from going too far in, and the overall length also differ. Choosing the correct blank is the first real decision in any key job.

Blanks come in many metals and finishes, and some have plastic heads, rubber covers or a spot for a chip. For homes, the most familiar blanks are brass or nickel plated brass. For vehicles, a blank may be a steel blade that matches a particular model line, sometimes with a place molded into the head for a transponder chip.

Because so many blanks look alike at a glance, mistakes happen at counters where a worker grabs the nearest match. A blank that is almost right may slide in, turn once and then bind. The fix is to match the blank by the markings on the key head, the shape of the keyway and the brand of the lock, and to test the finished key before you leave. A technician who comes to you can test it in the actual lock on the spot.

How a key turns into a working key

Inside a standard pin tumbler cylinder, small spring loaded pins sit in a row. Each pin has to be lifted to exactly the right height for the cylinder to turn. The cuts on the key push each pin to that height, one position at a time. If every pin lines up at the shear line, the cylinder rotates. If even one is off, it stays locked.

That is why cutting is a precision task. A cut that is a fraction too shallow or too deep leaves a pin out of place, and the key will feel gritty, stick or fail to turn. Our guide on how pin tumbler locks work shows the mechanism in more detail and explains why keys of the same style but different cuts are not interchangeable.

The cutting itself is done by a machine that follows either a pattern, such as an existing key clamped alongside the blank, or a set of numbers that tell the machine how deep to go at each position. Both methods can produce an accurate key. The difference lies in what the starting information is and how clean it is.

Cutting by copy versus cutting by code

When you hand over a key and ask for a duplicate, the machine traces the original and cuts the blank to match. That is simple to describe and, on a good original, reliable. The weakness is that any wear on the original is carried into the copy. A key that has been through years of daily use may have rounded edges, shallow valleys or small bends, and a copy of a copy slowly drifts away from the intended pattern.

A simple rule helps: always copy from the cleanest key you own, not from the one you carry every day. The daily key has taken the abuse, and the spare that has lived in a drawer usually has crisper edges. If you have only the worn one, say so, because a technician can sometimes compensate or suggest a code based approach instead.

Cutting by code works differently. A key code is a short series of numbers that describes the cut depth at each position. Given the code and the correct blank, a technician can cut a fresh key that matches the factory pattern, even if no original key is available. The result is a sharper, cleaner key than a copy made from a worn one.

Neither method is automatically right for every situation. Duplicating is practical when you hold a good key. Code cutting is useful when the original is missing, damaged or too worn to trace. A careful locksmith decides which to use based on the condition of what you hand over, and explains the choice to you.

Climate plays a small part too. In a humid, salt touched place like Miami Dade, brass keys and cylinders can tarnish and collect residue, which makes tracing less exact and keys feel stiff. A key that has spent years on a ring near the coast may look fine and still be a poor pattern to copy. See the guide on salt air and lock corrosion for what that does to hardware.

What a key code is and where it comes from

A key code is the number sequence that records how a key is cut. Each digit usually stands for a depth at one position along the blade, so a code is really a compact description of the lock's combination. Manufacturers assign codes when they build a lock or a vehicle and keep records tied to a serial or identification number.

Codes come in several flavors. Some are bitting codes that describe the exact depth at each cut. Others are reference numbers that a lookup system turns into bitting. Some codes are stamped on the lock, on a tag, or on paperwork that came with it. Vehicles often use data tied to the vehicle identification number, and a locksmith with proper access can retrieve the information after proof of ownership.

Because a code can reproduce a working key, it is sensitive information. Treat it like a spare key. If you have one written down, keep it somewhere private, not on a sticky note near the door it opens. The same care applies to photos of keys, which can reveal cut patterns to anyone who sees them.

Be cautious about sharing codes over messages or posting them in group chats, even with people you trust. A message can be forwarded, a phone can be lost, and a code never expires the way a temporary entry code on a keypad does. When you do need to pass one along, give it only to the person who will act on it and only for the purpose at hand.

• A code describes the cut depths, so anyone holding it can have a key made.
• A record of the code can replace a missing original when ownership is shown.
• Codes for cars generally require a legitimate request and proof of ownership.
• Codes for building locks should be kept by the property manager or owner, not posted on keys.

Why records matter more than most people think

Imagine losing every key to a property and having no record of how the lock was set up. The cylinder can still be worked on, rekeyed or replaced, but the process takes more steps. Compare that with a situation where the owner has the original codes or a clean key kept in a safe place. Making a fresh key becomes straightforward.

Records are especially useful in places with many locks. A multi family building, an office suite or a small business may have dozens of cylinders, some keyed alike and some not. Without a map of which key opens which door, every change becomes a small investigation. The guide on business key control policy shows how to keep that map useful.

At home, the record can be simple. Note which locks are keyed alike, how many keys exist, who has each one, and when the cylinders were last rekeyed. That small habit makes future decisions easier, such as whether to rekey or replace locks after a move or a change of tenants.

Restricted and high security blanks

Not every blank is freely available. Some keyways are restricted, which means the maker only sells blanks to authorized dealers, and copying requires a card or other authorization tied to the owner. The goal is to stop casual duplication by anyone with access to a key for a few minutes.

High security keys can also look different. Some have cuts on the sides rather than the top edge, some have a dimple pattern drilled into the flat of the blade, and some use extra moving parts in the cylinder. They resist wear better, cost more to duplicate and often need specific machines. If your key says do not duplicate, do not assume that is a bluff, because it might be backed by a controlled system.

When you hold a key like this, tell the technician before anything else. The page on key duplication and high security keys gives a broader view of what that work involves. Do not be surprised if the process asks for identification or for the original authorization card.

If you manage a building, restricted keys are worth a look. They help you know that when a key leaves a tenant's hands, it cannot be casually copied at a corner shop. The tradeoff is that you need to keep the authorization paperwork safe, because losing it makes legitimate duplicates harder for you too. The comparison between master key and keyed alike systems covers how such systems are organized.

Car keys, blanks and codes

Vehicle keys add a layer. The blade is cut from a blank made for that maker and sometimes that model range, and many blades follow a pattern that depends on the year and trim. The code may be derived from the vehicle identification number or stored in a manufacturer database that technicians can reach with the right credentials.

On top of the cut, most modern vehicles check a chip or an encrypted signal, so a perfectly cut blade is only half the work. The guide on car key types sets out the four common styles and what each one involves. A technician typically cuts the blade, then programs the chip or fob so the vehicle accepts it.

If you are replacing a lost car key, be ready to show proof of ownership. That might be registration or a title, plus your identification. This step protects you. Anyone able to get a key to your car with only a phone call would be an equal opportunity for a thief. The page on car key replacement covers the general process.

Wear, bent keys and keys that stop working

Even a perfectly cut key can fail over time. Edges round off, valleys fill with dirt and grit, and the metal can bend if used as a lever or a screwdriver. A key that sticks, catches or needs a jiggle to turn is telling you something. It might be the key, the cylinder or both.

Before making a new copy from a tired key, consider having the key checked. A fresh cut from a code or from a clean original often solves what looks like a lock problem. If the new key sticks in the same way, the cylinder may be dirty or worn, and cleaning or a replacement may be the right step. Our guide on what to do when a key will not turn explains how to tell the difference.

Never force a key that does not want to turn. Extra pressure can bend the blade or snap it inside the cylinder, which turns a small annoyance into a bigger repair. If a key is stuck or has broken, stop and call for help instead.

If a piece of key has already snapped off, do not try to dig it out with a pin or a knife. That pushes the fragment deeper and can scratch the pins. Leave the cylinder alone, keep the broken pieces, and describe the situation. The page on a key broken in the lock explains what the repair usually looks like.

Questions worth asking before any key is cut

A few plain questions at the start prevent most problems later. Which blank are you using, and does it match the keyway on my lock? Will you cut from my key or from a code? Will you test the finished key in the lock itself? If the answer to any of these is a shrug, it is reasonable to pause.

It also helps to ask what happens if the key does not work. A good provider stands behind the fit of the cut and corrects it on the spot, because the whole point of a visit is a key that turns smoothly. You should leave knowing the key was checked with you present, not hoping it will work when you get home.

Finally, ask about records. If you want a code kept for you, say so and ask how it will be handled. If you would rather nothing be kept, say that. Your wishes about your own lock information are legitimate, and a good technician respects them.

Making good copies and keeping them useful

A few habits keep your keys in good shape. Make spares from a clean original, not from a worn copy. Test each new key right away in the lock it belongs to, at least a few times, with the door open so you are not trapped if something is wrong. Label spares with a private mark, never with an address.

Keep track of how many keys exist. When a tenant leaves, a contractor finishes, or a relationship changes, the number of keys still floating around matters. If you cannot account for them, rekeying resets the situation without replacing the whole lock. The article on spare key strategies goes through where to store them.

Finally, tell your locksmith what you want. If you want copies that match the original exactly, say so. If you want the ability to make future copies from a code, ask whether a record can be kept in your own files. Plain requests lead to better results than assuming the person knows your plans.

What to expect from Home Advisor Locksmith

When you call about a key job, a real person answers and asks what you have. Describe the lock, what kind of key you hold, whether any original keys remain, and where you are. The price is explained upfront, before the truck rolls and before any blank is cut.

The technician comes to you, which matters when the key problem happened at a car, a gate or a business that cannot easily be left. Work is checked with you before the visit closes, so you can try the new key in the lock yourself. If something does not feel right, say so on the spot.

For more complicated situations, such as a lock with unknown history or a restricted key, expect a few extra questions. They are not there to slow you down. They make sure the right blank is used, the right records are consulted and the right person is asking. You can also browse the guides section for related topics before you call.