Keyways and key blanks, explained

A lock has an opening in its face where the key goes. That opening is not a plain slot. It is a shaped channel with ridges and grooves, and the cross section of that channel is called the keyway. Looking straight into a lock from the front, the keyway is the profile you see.

A key blank is the uncut key before any teeth are made. It has the same side profile as the keyway it is meant for, with ridges and grooves running along the blade. Think of it like a mold and a casting. The blank has to match the keyway shape or it cannot slide in at all.

Everything else follows from those two shapes. Cutting turns the blank into a working key by adding the specific notches that lift the pins to the right height. But before cutting even matters, the profile has to be right. This is why the right blank is the first step in making any key, and why a key that looks close can be completely useless. People are often surprised when a key from a drawer slides into a lock and refuses to turn. Sliding in only proves that the profile is close enough to pass the entrance. It says nothing about whether the cuts are right.

A keyway does two jobs. First, it guides the key in a straight line and holds it in position while it turns. Second, it filters out keys that do not belong. Only a blank with the matching profile can reach the pins at all, so a wrong key stops at the entrance.

The ridges and grooves along the blade interact with ridges, called wards, inside the keyway. Wards are fixed projections that stick out into the channel. A key blade must have matching grooves that let it pass around them, much as a person with the right shoulders can pass through a narrow doorway. A key with the wrong grooves hits a ward and stops. This is the oldest form of key control. The simplest locks, with only wards and a single bolt, relied on it entirely, and they could be opened by any key shaped to clear the wards.

Modern pin tumbler locks add a second filter, the pins, which respond to the cut pattern on the key. The keyway filters by shape, the pins filter by depth. A key must pass both. Our guide on how a pin tumbler lock actually works describes the pin side of the story in detail.

A typical house key has several parts. The bow is the head you hold. The shoulder is the flat step where the blade begins, and on many keys it acts as a stop that sets how far the key goes in. The blade is the long part that enters the lock, and the tip is the end.

Along the blade runs the profile, the pattern of grooves that matches the keyway. On the edge, or edges, of the blade are the cuts, the notches that interact with the pins. On a blank the edge is smooth and uncut, which makes it a blank. After cutting, the edge shows the series of peaks and valleys unique to that key.

Many blanks have a code stamped on the bow. This code names the blank type or the keyway, and it helps a locksmith find the right match. Some blanks are made in a family, with several closely related profiles, so choosing the right one calls for care. A blank that is almost right may enter but jam, or may turn poorly. For this reason a locksmith usually holds many blank types and checks each against the lock or the original key before any cutting begins, rather than trusting a catalog entry alone.

Locks come in families, and the keyway is what defines each. Some are wide and simple, some narrow and complex, and some are specific to a manufacturer. Residential locks often use a small set of common keyways, which is why a hardware store can cut a copy for many houses. Business and high security locks often use less common ones.

The more complicated a keyway is, the harder it is to get a matching blank. Some keyways are restricted, which means the blanks are controlled by the maker and sold only to authorized dealers. A restricted keyway adds a layer of control over who can make copies. Our guide to restricted keys explained looks at how this works in practice.

Keyways also change over the years. A building with an old lock may have a keyway that is no longer common. In that case, replacing the cylinder with a current one may be more practical than hunting for a blank. A locksmith can identify the keyway and tell you which route makes sense. In a rural area, where the nearest supply counter may be far away, a mobile locksmith who carries a range of blanks can often settle the question at the door.

• The keyway is the shaped opening in the face of the lock.
• A blank must match the keyway profile before cutting matters.
• Some keyways are common and some are restricted.
• A stamped code on the bow can help identify the blank.
• Old or unusual keyways may be easier to replace than to match.

Cutting is the step that gives the key its identity. In a pin tumbler lock, each pin stack sits at a specific height, and the key must lift each stack to the line where the plug can rotate. The cuts are small valleys of varying depth along the edge that do this lifting.

The depths are chosen from a set of standard steps. A key might use six positions along the blade and several possible depths at each position. The combination of those depths is called the bitting. Two keys with the same bitting open the same lock. A change of one depth in one position makes a different key. This is why a copy that is off by a small amount in one position can feel nearly right and still fail. The pins in the lock are unforgiving, because a pin that sits a little too high or low blocks the plug from turning.

Cutting can be done by following a code or by copying an existing key. In code cutting, the locksmith uses a depth and spacing chart and a machine that makes each cut. In duplicating, a machine traces the old key and cuts a new blank to match. Copies of copies can drift, which is explained in why duplicate keys sometimes fail.

Not all keys are the traditional edge cut kind. Some use a track milled into the flat side of the blade, a style often called a laser cut or sidewinder key. The cuts are inside the blade, not on its edge. The blank for such a key is thicker and has a different profile, and cutting requires a machine designed for that style.

Some keys have dimples drilled into the face. These are cut by a different type of machine. Other keys, such as those for certain high security cylinders, have extra elements such as sidebars that respond to features on the key. A blank for these systems often comes from a controlled source.

Car keys add another layer. Many are blanks with a built in transponder chip in the bow, and the chip must be matched to the vehicle before the car will start. Our article on transponder keys explained and the overview of car key types in plain words cover the electronics, which have nothing to do with the cut but depend on the blank.

Two blanks can look nearly identical and still be different in ways that matter. The width of a groove, the angle of a ridge or the length of the blade may differ slightly. A blank that is a little too thick will not enter. One that is a little too thin may wobble, turn poorly or wear the pins unevenly.

Length is a common trap. The shoulder or the tip sets how far the key sits in the lock. If a blank is longer or shorter than it should be, the cuts will line up with the wrong pins even though the depths are right. The key may feel as if it goes in all the way but never quite lifts the pins as needed. This is particularly common with keys that stop on the tip instead of the shoulder, where a small error in length shifts every cut by the same amount.

This is why a locksmith checks a new key by trying it in the lock and not just by comparing shapes. A key must slide in smoothly, turn without force and come out cleanly. If it sticks, drags or needs to be jiggled, the blank, the cut or both need attention. A good locksmith will not hand over a key that needs coaxing, because a key that needs coaxing will eventually fail on a cold morning or at the end of a long day.

When a key is lost, the blank is still the starting point. A locksmith can identify the keyway by looking at the lock. With the keyway known, the right blank is chosen. The cuts can then be found by reading the lock itself, using the pins, or by a code recorded when the lock was made.

Where a code is available, the locksmith can cut a key without taking the lock apart. Where it is not, the cylinder can be read or rekeyed, which means it is rebuilt to work with a new key from a fresh blank. Both routes lead to a working key. Which one is right depends on the lock and your goals.

If you lose a key you do not want anyone else to use, rekeying is the cleaner path. It changes the pins, so old copies stop working. See our rekeying service page. For a vehicle with a lost key, see car key replacement and the guide on what to gather when you lose every key.

A keyway is part of how a lock controls who can make copies. A common keyway can be copied almost anywhere, while a restricted or patented keyway can be copied only with permission. That difference matters to a business that wants to know who holds keys, or a property manager with many doors.

Keyways also relate to master key systems, where more than one key opens a given lock. These systems rely on careful planning of pins, and the keyways often belong to a family chosen for the building. If you manage a building with many locks, a plan for keyways and blanks is part of key control. Read what a master key system is for the bigger picture.

Remember that a keyway is not a security measure by itself. It narrows the range of keys that fit, but it does not make a lock unbreakable. A good lock combines a sound keyway, quality pins, a solid door and a strong strike. Treat the keyway as one layer, and look at the whole door. A restricted keyway on a flimsy frame still leaves a weak entrance, and a high quality door with a common keyway can be strong if the frame and the strike are sound. Balance matters more than any single feature.

When you need a new key, bring the original if you can. A clean, unworn original gives a cleaner result. Tell the locksmith what the key is for, whether it is a house, a shed, a padlock or a vehicle, because that helps identify the blank. If you only have a worn copy, say so.

Test each new key right away. Try it in the lock several times, with the door open and then with the door closed. A key that does not work smoothly on the day you receive it will not improve. If something is off, it is easier to correct the cut that day than to chase the problem months later when no one remembers where the key came from. Return it and have it cut again or checked.

Keep track of your keys, and keep one uncut spare of any special blank if you can obtain it, since a hard to find blank can be the slowest part of replacing a key. Label the ring with a code rather than an address. Store spare keys safely, as described in storing spare keys safely. When you need help, our key programming and automotive locksmith pages explain what we do, and you can reach us through the request form. Our van carries key cutting equipment and a range of blanks.