Locksmithing -- Warded Locks

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The warded lock is the oldest lock still commonly in use and is found in all corners of the world. It employs a single or multiple warding system. Because of its simple design, its straightforward internal structure, and its easily duplicated key, this lock is an ideal training aid for locksmiths. This same simplicity means that warded locks give very little security. Use these locks only in low-risk applications such as storage sheds and rooms where high security isn't essential.

At one time warded locks were used on most doors. They are still found in abundance in buildings still standing in older metropolitan neighborhoods such as Center City Philadelphia, Market Street in San Francisco, the Old Town section of Chicago, and the East Side of New York City.

The oldest of these buildings have cast-iron locks on the doors, some of which date back to the last century. Later locks were made of medium-gauge sheet metal. The casing consists of two stampings: the cover plate and the back plate. The latter mounts the internal mechanism and forms the sides.

The warded lock derives its name from the word ward, meaning to guard.

The interior of the lock case has protruding ridges or wards that help protect against the use of an unauthorized or improperly cut key. Normally there are two interior wards positioned directly across from each other on the inside of the cover and backing plates.

This lock is sometimes mistakenly referred to as a skeleton-key lock. The proper and full name is the warded-bit key lock.


Two types of warded locks are currently in use: the surface-mounted (or rim) lock and the mortised lock. While both types are similar in structure and size, they give a varying degree of security. The internal mechanisms of both operate on the same principle, but the mortise lock may have several additional parts. Differences between these locks are as follows:

+=+= Bit key locks are available in mortised (left) and surface-mounted styles. (Taylor Lock Co.)

Surface-mounted (rim) lock Mortised ward lock Mounted on door surface Mounted inside of door Secured by screws in the door face Secured by screws in the side of the door at the lock face plate Door can be any thickness Door must be thick enough to accommodate Thin case Fairly thick case Short latchbolt throw Up to 1-inch latchbolt throw Lock from either side Locked from either side Strike can be removed with door closed Strike cannot be removed with door closed Very restricted range of key Restricted range of key changes

Very weak security | Weak security


The basic interior mechanism is shown. Since the relative security of any lock lies in the type of key used, the number of key variations possible, and the amount of access to the locking mechanism afforded by the keyhole, the warded lock is the least secure.

The keyhole is an access route to the interior mechanism of the lock. The larger the keyhole, the easier it’s to insert a pick or other tool and release the bolt.

If a lock was designed to have no more than 10 different key patterns (changes) and 1000 locks were made, 10 different keys would open all 1000 locks. By the same token, one key would open the lock it was sold with and about 99 others. Furthermore, it’s often possible to cut away parts of a key to pass (negotiate) the wards of all 1000 locks. Notice that lock security is related to the kind and number of key changes built into the system when it’s initially designed.

+=+= The internal parts of a typical bit key lock.

+=+=The key on the right is for a lock activated from one side of a door; the key on the left can pass the wards from either side.

+=+= Case wards can be at many different positions.

In theory, each warded lock can be designed to accept 50, or even 100, slightly different keys. In practice, these locks tend to become more selective as they age and wear. The lock might respond to the original key or to one very much like it, but keys that would have worked when the mechanism was new no longer fit. While this might seem fine and well for the lock owner, excessive wear increases the potential of both key breakage within the lock and jams in the open, partly open, or closed positions. It can also mean that a new lock will have to be installed.

Most surface-mounted and mortised locks are intended to be operated from both sides of the door. Keyholes and doorknob spindle holes extend through both sides of the lock body. Occasionally you will encounter a surface-mounted lock with a doorknob spindle and keyhole only on one side. The other side is blanked off. A lock of this type can be modified to accept a key from the other side. This modification entails cutting a keyhole through the door and lock body and may require some filing on the key. +=+= the differences in keys. Note the additional cut on the left-hand key.


The key must be cut to correspond to the single or multiple side and end wards that have been designed into the lock. After the key passes these wards, it comes in contact with the locking mechanism. The cuts on the key lift the lever to the correct height and throw the deadbolt into the locked or unlocked position. Turning the doorknob activates the spindle and, so long as the deadbolt is retracted, releases the door.

+=+=depicts various keyhole control features that allow only certain types of cut keys to enter the keyhole. +=+= shows a key entering a keyhole.

Notice that the key has the appropriate side groove to allow it to pass through the keyhole and into the lock. If you were to file off this obstruction (called a case ward), any key thin enough to pass could enter. (Some ward bit keys are quite thick.) By the same token, a very thin key can pass whether or not the side ward is present. The common skeleton key is a prime example of this; it’s thin enough to pass most case wards but it won’t necessarily open the lock.

+=+= a key engaging the bolt. While there is only one set of wards in this particular lock, the positioning of this ward gives more security than a lock with no ward or one with a ward that has been worn down to almost nothing.

+=+= A slot milled on the edge of the key allows the key to pass the case ward.

+=+= A skeleton key is a key that has been ground down to bypass the case ward.

+=+= Even a single ward limits the number of keys that can operate a bit key lock.


Because it’s usually cheaper to replace them, warded locks are not repaired to any great extent. You should, however, have a supply of spare parts for these locks.

Broken locks:

The most frequent failure is a broken spring. Over a period of time, the spring may crystallize where it mates with the bolt. In addition, the wards can break or wear down into uselessness.

Replace a broken spring with a piece of spring stock cut to length and bent to the correct angle. Some spring stock must be tempered before use; other springs come already tempered. If tempering is necessary, heat the spring to cherry red, then quench it in oil. You can save time by purchasing standard springs already bent into a variety of shapes that are designed to fit almost all locks.

Worn or broken wards on locks with cast cases can be repaired by drilling a small hole in the case and forcing a short brass pin into the lock case. The best technique for brittle cases is to braze a piece of metal on the case at the appropriate spot and file it down to the appropriate size. Wards on locks with sheet metal cases can be renewed by indenting the case with a punch ground to a fairly sharp point. If the factory has already punched out the wards, it would be best to braze a piece of metal at the proper spot.

Since most of these locks are inexpensive and offer minimal security, you should remind customers that the cost of repair may far exceed the cost of the lock. Purchasing a new and more secure lock has definite advantages. If you are already at his or her home on a call, the homeowner can save money by asking you to install a new lock immediately instead of ordering one and having you make a second trip to install it.

Should the homeowner decide to take your advice and purchase a new lock, ask to keep the broken one; it’s of no use to him or her and parts are always nice to have. Sooner or later you will have to repair another lock of the same type; having the correct parts at hand will save you time. Furthermore, you have made a sale and, by being allowed to keep the old lock, have obtained parts at no cost.

Removing paint:

Removing paint from warded locks is also a form of repair. The home painter is a major cause of lock failure. He often does not take the time to remove the lock or to cover it with masking tape. Paint usually gets into the mechanism, freezing its works. To clean a paint-bound lock, follow this procedure:

Remove the lock from the door. (Run a sharp knife around the edges so the new paint won’t be cracked and broken.) Disassemble the lock. Using a wire brush, scrape the paint from the parts. In extreme cases, you may have to use a small knife or soak the individual parts in paint remover. Dry each part thoroughly. Check for rust and worn parts and replace as needed. Assemble and mount the lock.

Use paint remover only as a last resort because it leaves a residue that attracts dust and lint. When you use paint remover you must clean each part before assembly.

Lubricating locks:

Locks that are difficult to operate usually have not been lubricated in a long time, if ever. Never use oil to lubricate a lock. The professional approach is to use a flake or powdered graphite. Apply the lubricant sparingly. Remember, a little bit goes a long way. This is especially true of graphite. Should you overuse it, you may have to explain to the homeowner why there is a dark patch on the carpet that cannot be cleaned. Graphite stains are almost impossible to remove.

Warded Keys:

Warded keys are made of iron, steel, brass, and aluminum. Iron and aluminum keys have a tendency to break or bend within a relatively short time; steel and brass keys can outlast the lock. The warded key has seven parts. The configuration of the bow, length of the shank, and the relative thickness of the shoulder are not critical to the selection or the cutting of the key.

Types of warded keys Warded keys come in various types, including the simple warded key, the standard warded key, the multicutkey, and the antique key. Simple warded keys are often factory-made precut keys that fit several different keyholes. Multicut keys, on the other hand, are designed for specific locks. The standard warded key is usually mass-produced, but it has more precut ward and end cuts than the simple warded key. Standard warded keys can be easily converted into master keys by cutting. The antique key may have several kinds of cuts: ward cuts, end cuts, and even side (or bullet) groove cuts extending the length of the bit. Antique keys usually go to older locks, but these keys are still manufactured.

+=+=Parts of a bit key.

TABLE 1: Standard Wire Gauges (inches and millimeters). 1 mm =0.03937”; 1 inch = 25.4 mm Standard wire gauge number | Inches Millimeters|

Selection of key blanks:

A key blank is a key that has not been cut or shaped to fit a specific locking mechanism. When selecting a blank for a duplicate warded key, the following should be considered:

Post size. The post of both keys (original and duplicate) must be the same diameter. If your eyesight cannot correctly determine whether or not they are the same size, use either calipers or a paper clip. Use the calipers to compare the diameter of the original key with the diameter of the duplicate. You can use a paper clip that has been wrapped around the original key to check the diameter of the duplicate.

Length. From the collar to the end of the pin, both keys should be approximately the same length. This is important because this portion of the key enters the keyhole and operates the lock.

Height. The height of the bitting (cuts in the bit) must be the same on both keys. If the bitting in the duplicate is higher, it should be filed down; if it’s lower, another blank should be selected.

Bow. The bows need not be identical but generally should be closely matched.

Width. The width of the bittings should be approximately the same. If the bitting on the duplicate is too wide, the extra thickness may prevent the duplicate from entering the lock.

Thickness. The thickness of the bits should be the same. If the original key bit is tapered, the bit of the duplicate should also be tapered. You may have to select a blank with a thick bit that you can file down to the correct taper.

If you don't have a micrometer which shows standard wire diameters, can help you determine the approximate diameter of warded key blanks.

You can take a standard piece of wire with a known diameter and compare it with any key blank. Also, use a drill to determine the approximate diameter of warded key blanks. Insert the pin of a blank into the hole that matches the blank's diameter.

+=+=File into the aluminum strip in the direction shown.

Duplicating a warded key by hand:

1. Select the proper key blank.

2. Wrap a strip of aluminum approximately 1 1/2” _ 2 1/4” or 2 1/2” around the pin and bit of the original key with one edge against the collar.

3. Clamp the original key (wrapped in the aluminum) into a vise, bitting edge up. Ensure that the aluminum fits snugly around the key bit and pin.

4. Cut off excess aluminum around the bit of the key. Remove the aluminum strip and smoke the key with a candle.

5. Place the strip back on the bit and re-clamp.

6. Using a warding file, cut down the aluminum strip-not the original key- until it’s in the shape of the original key. Since the aluminum bends easily, use the file only in one direction-away from you. The stroke should be firm and steady at first. As you file closer to the cuts of the original key, the strokes should be shorter and lighter. When the file just barely touches the original key and starts to remove the candle black, stop and go no further. If the candle black is removed and the shiny surface of the original key is revealed, you have filed too deeply.

7. Fit the aluminum strip onto the key blank.

8. File down the exposed areas on the bit until it matches the outline of the aluminum strip. Be careful not to cut into the strip. Again, use shorter and lighter strokes as you get closer to finishing each cut.

9. If the original key has a side groove that matches a keyhole ward, this too must be cut. Use another strip of aluminum. If the original key has two grooves, you must wrap the strip around the bit so that both grooves are covered.

10. Using a scriber, scratch the metal strip to indicate the top and bottom of the groove(s). Fit the strip onto the key blank and mark the positions of the groove(s) on both ends of the bit. By connecting the marks with lines, you know exactly where to file.

11. To determine the depth of a groove cut, put one edge of a metal strip into the groove of the original key and scribe the depth of the groove on it. This mark will be your depth guide when filing the groove on the duplicate key.

Pass keys: Skeleton-type pass keys (master keys) are sold in variety stores. These keys will fit many old locks and more than a few new ones. As such, they are convenient. However, few locksmiths stock them. Why? Many locksmiths believe the ethics of the profession forbid it. You certainly don’t want to supply some one with a key that could open her neighbor's lock. Nor should you duplicate a pass key without authorization from the owner. Be leery of a customer who wants a key duplicated but with additional cuts. Locksmiths have lost their licenses for less. Don't let it happen to you.

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Updated: Sunday, March 24, 2013 9:35