Locks rank among the oldest building security devices, and they still decide who can enter a home while the owners sleep or travel. Locks also show up in less obvious places: cabinets holding cleaning products, luggage heading through an airport, and storage sheds full of tools. Choosing the right lock starts with the door itself, because a lock is only as strong as the frame and hardware around it. Before mounting anything, check that the door frame sits square and true, using the types of levels used in leveling a frame on any construction site. A frame that is out of square binds the latch, wears the strike plate, and makes even a high-grade lock easier to defeat.
How Lock Security Grades Work
Lock hardware is tested and graded under the ANSI/BHMA standard, which sorts locks into three grades. Grade 1 locks endure the most use and carry the highest price, Grade 2 suits busy residential doors, and Grade 3 covers basic residential hardware. The grade reflects cycle testing, impact resistance, and finish durability, so a Grade 1 deadbolt on a front door outlasts a Grade 3 model through years of daily use. Installation quality matters more than the sticker: a deadbolt on a sagging door fails early, so confirm proper leveling of the frame before you set the strike plate.
ANSI/BHMA Grades at a Glance
| Grade | Typical use | Durability | Price range |
|---|---|---|---|
| Grade 1 | Commercial and high-traffic residential doors | Highest cycle rating and impact resistance | $60 to $150 |
| Grade 2 | Busy residential exterior doors | Medium cycle rating | $40 to $90 |
| Grade 3 | Interior and low-traffic doors | Basic cycle rating | $15 to $50 |
Most homes need a Grade 1 or Grade 2 lock on exterior doors and Grade 2 or Grade 3 inside. A busy family entry earns a Grade 1 deadbolt, while a linen closet works fine with Grade 3.
What the Grade Does Not Cover
A grade rating covers the lock mechanism, not the door, frame, or hinges. A reinforced strike plate and a solid-core door raise real-world security more than moving from Grade 3 to Grade 1 alone. The grade also says nothing about key control, so a lock sharing a common keyway is only as secure as the people who hold those keys.
- Front and back exterior doors: Grade 1 or Grade 2 deadbolts.
- Interior bedrooms and bathrooms: Grade 2 or Grade 3 privacy locks.
- Closets, pantries, and cabinets: Grade 3 locks or cam locks.
The Main Types of Locks
Eight lock types cover almost every residential need, and the comparison below helps you sort them.
- Deadbolts secure exterior doors with a bolt that slides into the frame.
- Knob locks combine a latch with a keyway inside the knob.
- Lever handles offer an easier-to-grip latch for high-traffic interiors.
- Mortise locks carry latch and deadbolt in one unit set into the door edge.
- Cam locks protect cabinets, desks, and mailboxes.
- Padlocks bring a portable shackle to gates, sheds, and luggage.
- Smart locks use a keypad, app, or fingerprint reader instead of a key.
- Keypad locks deliver code entry without an app.
| Lock type | Best for | Key feature |
|---|---|---|
| Deadbolt | Exterior doors | Bolt slides into the door frame |
| Knob lock | Interior doors | Latch and keyway built into the knob |
| Lever handle | Accessibility and high-traffic interiors | Easy-to-grip lever |
| Mortise lock | Commercial and historic doors | Latch and deadbolt in one unit |
| Cam lock | Cabinets, desks, and mailboxes | Rotating cam latch |
| Padlock | Gates, sheds, and luggage | Portable shackle |
| Smart lock | Keyless entry and rentals | Keypad, app, or biometric access |
| Keypad lock | Doors where a code beats a key | Code entry without an app |
Entry points include the front door, the garage service door, and patio doors, which face weather and forced entry alike, so the lock you choose there should resist corrosion and tampering.
How to Compare Lock Types
Compare locks on four points: where the lock will live, how often it will be used, who needs access, and what the door is made of. An exterior door takes a deadbolt rated for weather exposure, while a home office door may only need privacy. The same comparison applies to rentals, where key control and rekeying costs decide between a classic deadbolt and a smart lock.
Match the Lock to the Threat
A lock deters casual entry, not determined burglary, so pair the hardware with a solid door, reinforced strike, and good lighting. Locks rated for exterior use resist rust and ice, which matters in wet climates. Interior locks prioritize privacy and convenience over brute strength.
Deadbolts and Knob Locks
Deadbolts are the standard for exterior doors because the bolt extends into the frame and resists forced entry better than a spring latch. Single-cylinder deadbolts open with a key outside and a thumb turn inside. Double-cylinder deadbolts take a key on both sides, which blocks entry through a nearby window but slows an emergency exit. Most residential doors are 1-3/8 or 1-3/4 inches thick, with a 2-3/8 or 2-3/4-inch backset from the door edge.
Single vs. Double Cylinder Deadbolts
Choose a single-cylinder deadbolt for the main entry and a double-cylinder only where glass sits within reach of the thumb turn. The trade-off is real: it defeats window break-ins but creates a fire risk if the key is not immediately available. Building codes in many areas restrict double-cylinder locks on egress doors for that reason.
Reinforcing the Strike
The strike plate is where the bolt meets the frame, and a short-screw strike plate fails first under force. Replace it with a reinforced plate and 3-inch screws that reach into the framing studs. On masonry exterior walls, the surrounding construction, from the types of bricks to the mortar joints, determines which anchors hold the strike plate securely.
Knob locks use a spring latch inside the knob and work well for interior doors, but they should not secure an exterior door on their own. A determined push or a well-placed kick can defeat a spring latch, which is why exterior doors pair a knob lock with a deadbolt or skip the knob lock entirely. Privacy knob locks, opened from the outside with a small tool, suit bedrooms and bathrooms.
Mortise Locks and Lever Handles
Mortise locks cut a pocket into the door edge and house the latch, deadbolt, and handle mechanism in a single steel case. The construction is heavier than bored cylindrical locks, which makes mortise locks common in commercial buildings and older homes. They cost more and need a precise cut, but they operate smoothly for decades when maintained.
Lever Handle Functions
Lever handles come in three functions: passage levers turn freely without locking, privacy levers lock from the inside, and keyed levers take a key outside. Levers are easier to operate than knobs for children, older adults, and people carrying groceries, which is why accessibility standards favor them. Exterior doors use a keyed lever or a lever with a deadbolt.
When to Choose a Mortise Lock
Choose a mortise lock for high-traffic doors, historic hardware, or a project that already needs the door edge machined. Retrofit is the catch: installing a mortise lock into a door cut for a cylindrical lock means patching the old holes and cutting a new pocket, work best left to a skilled carpenter. Like other building components, locks experience the same types of failures that affect construction materials, and a mortise lock is easier to rebuild than replace.
Cam Locks, Padlocks, and Specialized Locks
Cam locks secure small compartments. The cylindrical base holds a keyway, and turning the key rotates a metal cam into the locked position. They are light-duty by design and perfect for cabinets, desks, tool chests, and mailboxes.
Padlocks carry security wherever there is no permanent lock. A hardened steel shackle resists cutting, and the body material ranges from laminated steel to brass. Match the shackle length to the hasp and the body size to the risk: a small padlock deters casual theft from a gym locker, while a heavy shrouded-shackle model protects a shed or gate. For travel, TSA-recognized padlocks let screeners open luggage without cutting the lock.
Child safety locks keep young children away from cleaning products, medicine, and pest treatments. These small devices mount inside cabinet doors and release with a pinch or a magnet. They are not security locks in the burglary sense, but they matter in a house with toddlers.
The most visible security on any building is its door locks, and exterior-rated models handle weather far better than interior hardware. On gates and outbuildings, a weatherproof padlock or keyed hasp gives the same protection with less installation work.
Choosing a Padlock by Shackle Size
Measure the hasp opening before buying. A shackle that is too short will not fit, and one that is too long invites a pry bar. Shrouded shackles resist bolt cutters, and disc-style padlocks resist picking better than pin-tumbler models at the same price.
Child Safety Locks
Magnetic locks require a strong magnet to open and mount out of sight, while pinch-style locks sit inside the cabinet. Both install with screws or adhesive, and adhesive versions leave no holes when the kids grow up. Test the release before trusting it with a curious toddler.
Smart Locks and Matching Locks to Your Building
Smart locks swap the keyway for a keypad, a phone app, or a fingerprint reader. They shine in rentals, where owners issue temporary codes instead of copying keys, and in busy households that lose keys regularly. Most smart deadbolts retrofit into the same backset holes as a standard deadbolt, so the upgrade takes a screwdriver and an hour.
Smart Lock Features to Compare
Compare battery life, backup access, and connectivity before buying. A smart lock that dies with the owner locked out needs a physical key backup or a 9-volt jump terminal. Wi-Fi models report status remotely but drain batteries faster than Bluetooth-only models. Check that the lock fits the door’s existing deadbolt holes and that the app supports the household’s phones.
Battery Life and Backup Keys
Most smart locks run six months to a year on AA batteries, depending on how often the motor cycles. Keep spare batteries near the door and test the manual keyway when you change batteries. A lock with no backup key and no jump terminal is a lock you can get locked out of.
The best lock depends on the building type and the door’s job. Apartments and rental units favor smart locks for key control, single-family homes lean on deadbolts and reinforced strikes, and outbuildings get by with padlocks. Match the grade to the traffic, the mechanism to the door, and the features to the people who live there, and the right lock does its quiet job for years.