When it comes to advancing your physical security, it can sometimes be a daunting task as at first glance there appears to be an infinite number of different types of locks.

And even more disheartening, trying to determine the degree of security these different locks offer.

But in truth, all locks are very simple creatures in theory and shouldn’t be feared.

The purpose of this guide is to aid you in two ways: to help determine what types of locks could best suit your needs and to enlighten you of what security considerations to be aware of for each lock type.

Additionally, we provide a recommendation for each lock type as can be found by clicking the images associated.

Types of Locks

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Padlocks

Padlocks are typically never permanently attached to anything and are the only lock type that is portable. They utilize a shackle to secure the item of interest and come in an array of sizes. There are typically two styles of padlocks - keyed and combination - and both possess three main components: the body, the shackle, and the locking mechanism.

Keyed padlocks, as the name suggests, utilize a key to disengage the locking mechanism.

These can either be key-retaining or non-key-retaining locks. Key-retaining padlocks don’t allow for the key to be removed while the lock is open.

Non-key-retaining locks, on the other hand, do allow for key removal while the lock is open. In addition, keyed padlocks can sometimes be re-keyable meaning that the key cylinder can be removed and replaced with a new one allowing you to use a new key.

Padlocks are very easily compromised as they can be broken by force - such as bolt cutters, hammers, or drilling - or bypassed by more subtle means such as lock picking or shimming.

Combination padlocks utilize a series of numbers that opens the lock when they are entered in the correct sequence. These locks suffer the same weaknesses as keyed padlocks but additionally can be decoded through means of combination cracking, such as cracking a Master Lock.

Knob Locks

Knob locks are most commonly found in residential homes as the primary locking device on both internal and external doors. These locks have a key cylinder located on one side and a rotatable knob on the other that controls the locking mechanism. When utilizing these locks on external doors they should always be accompanied by a secondary lock - such as a deadbolt - as they are very easily compromised to brute force attacks. All it takes is a hammer to knock off the knob and pliers to disengage the locking mechanism for someone to bypass these locks. They are also very prone to lock picking and shimming.

Deadbolts

Deadbolts are most commonly found on external doors to residential homes and are usually accompanied by a knob lock. Deadbolts utilize a rotating cylinder that drives a bolt into the door frame that can not be retracted until the locking cylinder is once again rotated.

These locks are much more resilient to brute force attacks and are impervious to shimming, but can fall victim to lock picking. Because these locks usually employ a pin tumbler locking mechanism you can test the security of your deadbolt through learning lock picking. There are three variations of the deadbolt: the single cylinder, double cylinder, and lockable thumb turn.

Single-cylinder deadbolts are what you most commonly see in residential homes. These locks have two separate methods of activating the locking mechanism. On one side you have a key cylinder and on the other side, a rotating thumb turn. The double cylinder deadbolt, on the other hand, uses a key cylinder on both sides of the lock. These locks are a potential fire hazard as you need the key to unlock the door from the inside.

The final variation of the deadbolt is the lockable thumb turn. This deadbolt is similar to the single-cylinder whereas it has a key cylinder on one side and a thumb turn on the other. The only difference is that the thumb turn has a lockable key cylinder on it allowing you to lock the thumb turn. These locks give you the advantages of both the single and double cylinder deadbolts.

You can significantly increase the security of your deadbolt by installing a flip guard. These nifty devices have a latch that flips over the turn knob of the deadbolt and restricts it from rotating. As a result, the deadbolt becomes immune to lock picks, bump keys, and even a key from the outside. Flip guards can be installed in minutes and are a relatively cheap investment for such a huge security boost.

Lever Handle Locks

These locks are usually found on the inner doors of commercial buildings. They use a lever that can either swing up or down to release the bolt. Just like knob locks they have a key cylinder on one side and a rotatable turn knob on the other.

Because they use a lever they are extremely easy to open which makes them perfect in a commercial environment and handicap accessible areas.

These types of locks can be compromised through the use of lock picking and brute force-torque attacks, such as abruptly applying all of your weight on the lever. However, some lever hand locks do employ "clutch" levers that won't place pressure on the locking mechanism if force is applied to the lever while locked.

Cam Locks

Cam locks are a style of latch that are commonly used in filing cabinets, lockboxes, and other low-level security appliances. These locks utilize a small flat metal tailpiece called a “cam” that uses a key to rotate the cam into and out of a slot in the door.

They can rotate either clockwise or counterclockwise and there is quite the variety of cams that can be used. Cam locks typically employ either a pin tumbler or tubular locking mechanism, both of which are exceedingly simple to pick.

Mortise Locks

The mortise lock utilizes two different lock types compiled into one device. It first includes a non-locking sprung latch that is controlled by a lever handle. Additionally, it has a deadbolt that is used as secondary security.

These locks are dual-action meaning that they act as both a doorknob and a deadbolt. Mortise locks take much more skill to install than a traditional knob lock or deadbolt but are significantly stronger locks. Just like a common deadbolt they are susceptible to lock picking but put up a greater defense to forced entry.

Euro Profile Cylinders

Euro profile cylinders are most commonly found in residential homes and other locking devices throughout Europe and Asia. They can also be found in some sliding doors in North American.

There are three varieties of these locks: single cylinder, double cylinder, and single cylinder with a thumb turn. Single-cylinder uses a key or rotating thumb turn on one side that actuates the locking mechanism.

You will likely see these in sliding doors that can only be locked and unlocked from the inside. The double cylinder, like a deadbolt, uses a key to control the locking mechanisms from both sides of the lock. And similar to the deadbolt, there is also a variety that utilizes a locking cylinder on one side and a rotatable thumb turn on the other.

These locks are prone to a particular style of brute force attack called lock snapping. In addition, if the lock is not the proper length for the thickness of the door it can make it much easier for a perpetrator to utilize this method of lock snapping.

While some - like the Yale Anti-Snap as shown to the left - provide a snap-off front section to protect against such attacks, they are still always powerless against lock picking.

Jimmy Proof Deadbolt

Jimmy Proof deadbolts are commonly found in older apartments and double doors. These locks are surface mounted on the inside of the door and are very easy to install.

The idea behind the creation of these locks was to prevent burglars from meddling with the deadbolt locking mechanism and gaining entry by simply prying apart the door frame with a crowbar. These types of locks use two interlocking vertical bolts that fall into a strike plate when the lock is engaged.

Jimmy Proof deadbolts usually utilize a single cylinder that uses a key on one side and a turnable knob on the other.

Additionally, these deadbolts sometimes have a unique toggle that allows you to lock the deadbolt so that even a key can not disengage the lock from the outside. This secondary lock makes these locks impervious lock picking.