Most US exterior doors use one of five types of door locks: a deadbolt, a keyed knob or lever, a handleset, a mortise lock, or a smart lock. The rule for choosing is short. The deadbolt is the part that resists force. Everything else either latches the door shut or repackages a deadbolt inside a different body. So the real question is not which type is best. It is which type your door is already prepared for, and whether there is a deadbolt above the knob at all.
That framing matters because most pages answering this query are not written for a US door. If you are reading about mortice locks, nightlatches and sashlocks, you are on a British page, and those are not the products at your local hardware store. This guide covers the US residential set only.
The rest of this cluster
This page frames each type and hands the detailed answer to a dedicated guide. Those guides cover: what ANSI/BHMA grades actually test, single versus double cylinder deadbolts and the code question, how to measure backset and bore before you order, why the jamb fails before the lock does, why a keyed knob is not security, mortise versus cylindrical locks in older homes, privacy versus passage versus keyed entry, the three inch strike screw fix, whether you want a handleset, locks for steel and fiberglass doors, and the smart lock pillar. Links go in as each one publishes.
First, identify what you already have
Before you compare products, measure the door. Two minutes with a tape measure rules out most of the wrong purchases, because US residential doors are machined to a standard preparation and locks are sold to match it.
Schlage's own door preparation checklist gives the numbers for a standard bored door. The cross bore, the large hole through the face of the door, should measure 2-1/8 in. in diameter. The latch bore, the hole in the edge of the door where the bolt travels, should measure 1 in. The backset, measured from the edge of the door to the center line of the cross bore, should read either 2-3/8 in. or 2-3/4 in. The door itself should be between 1-3/8 in. and 1-3/4 in. thick. In the frame, the strike bore should be at least 7/8 in. across and at least 1/2 in. deep.
Then count the holes. One hole means a knob or lever only. Two holes stacked vertically means a knob or lever plus a deadbolt, and the spacing between them decides whether a one piece handleset will drop in. A long rectangular pocket cut into the edge of the door instead of a round bore means you have a mortise lock, and you are shopping in a different category entirely.
Deadbolts
A deadbolt is a solid bolt thrown by a key or a thumbturn. It does not retract under spring pressure, which is why it is the security component on the door and the knob is not. Two variants exist for US homes. A single cylinder deadbolt takes a key outside and a thumbturn inside. A double cylinder deadbolt takes a key on both sides.
The double cylinder version is the one that needs care. The International Residential Code, Section R311.2, requires that the egress door be readily openable from inside the dwelling without the use of a key or special knowledge or effort. A lock that needs a key from the inside conflicts with that language, and jurisdictions differ in how they apply it and where they allow exceptions. Your local building department is the authority for your address, not a product listing. The cylinder guide in this cluster covers what the code says and what to ask them.
Bolt throw length is the other spec worth knowing, and it is the one most listings bury. Longer bolts reach further into the frame. That guide is scheduled separately.
Keyed knobs and levers
A keyed knob or lever is a latch with a key in it. The bolt is a spring latch with an angled face, which is what lets the door click shut when you push it. That angle is the point: the latch is designed to give way under pressure so the door can close, and a short spring latch in a shallow strike is not a forced entry barrier.
Levers are the same mechanism in a different shape. They are easier to operate with full hands or limited grip strength, which is why they are common on interior and accessible doors. Nothing about the lever shape changes the security picture.
The practical takeaway for an exterior door is that a keyed knob alone is an incomplete setup. The knob controls who can casually open the door. The deadbolt above it is what carries the load. If your front door has one bore and a keyed knob in it, the upgrade that matters is adding a deadbolt, not buying a nicer knob.
Handlesets
A handleset is the tall entry unit you see on front doors: a decorative exterior grip plate with a thumb lever, usually paired with a deadbolt above it, sold as a matched assembly. Some are a genuine single unit; many are simply a knob or lever set and a deadbolt sharing one exterior escutcheon.
What you are paying for is mostly appearance, matched finish and a one piece exterior look. The security still comes from whichever deadbolt is in the package, graded the same way a standalone deadbolt is graded. A handleset does not add a security category.
The compatibility catch is spacing. Because a handleset spans both bores, the center to center distance between your knob bore and your deadbolt bore has to match what the handleset was made for. Measure it before ordering. The handleset comparison guide in this cluster goes through the sizes.
Mortise locks
Mortise locks predate the bored door. Instead of two round holes, the door is cut with a deep rectangular pocket in its edge, and a metal case containing both a latch and a deadbolt slides into that pocket. You will find them in older US homes, in heavier doors and in some commercial style entries.
If you have one, you have three routes. Replace the case with a modern mortise lock body sized to the same pocket, which keeps the door intact. Rekey or service the existing case, which is often the cheapest option if the body still works. Or convert the door to a standard bored preparation, which means filling the pocket and boring new holes, and is the route that changes the door permanently.
Mortise bodies are not interchangeable by brand, and the pocket dimensions, the backset and the position of the cylinder and handle hub all have to match. This is the one lock type where measuring first is not optional. The mortise versus cylindrical guide walks through identification.
Smart locks
A smart lock, on a US front door, is usually still a deadbolt. That is the useful way to think about it. It sits in the same 2-1/8 in. cross bore, uses the same backset, has to fit the same door thickness range, and is graded under the same residential hardware standards as a mechanical deadbolt.
Two install types exist. A retrofit smart lock replaces only the interior thumbturn and drives your existing deadbolt, so your existing key and exterior cylinder stay. August built its reputation on that design. A replacement smart lock swaps the whole deadbolt, exterior cylinder or keypad included, which is what Schlage, Yale and Kwikset mostly sell.
The choice is a door and tenancy question first. Renters and anyone who wants to keep an existing key system usually want retrofit. Anyone who wants a keypad on the outside needs replacement. Whether it talks to your phone, your hub or your rental platform is a separate question, and a separate guide.
Interior doors: privacy, passage and dummy
Interior hardware is sold by function, and the three words on the box mean specific things. Passage hardware has no lock at all and simply latches. Privacy hardware locks with a button or turn on the inside and has a small emergency release hole on the outside, which is what bedroom and bathroom doors use. A dummy is a fixed handle with no mechanism, mounted for looks or as a pull on a closet or an inactive door.
Privacy is not security hardware and is not sold as such. The emergency release exists on purpose so an adult can get into a bathroom where someone has fallen. If you want an interior door that resists more than that, you are looking at keyed entry hardware, and the interior door guide covers where that is and is not sensible.
What the grade on the box means
US lock packaging carries two different grading systems, which is why the pages explaining them contradict each other. The older ANSI/BHMA numeric grades run 1, 2 and 3, with Grade 1 highest, and come from the A156 series of standards published by the Builders Hardware Manufacturers Association. Residential hardware has its own documents in that series: A156.39 for residential locksets and latches, A156.40 for residential deadbolts and deadlatches, which BHMA describes as covering durability, security and finish tests. Alongside those, BHMA's Certified Secure Home labeling grades a residential lock separately in three categories, Security, Durability and Finish, using letters where A is best, so AAA is the top combination. Schlage's consumer page describes the same three categories.
So a Grade 2 and a AAA are not two points on one scale. Ask which system a claim is using before comparing two products. For most houses, a Grade 2 deadbolt with a properly fastened reinforced strike is a sensible default, and the money that would go into a Grade 1 upgrade often does more in the frame. The grades guide in this cluster works through what each test actually measures and where the published cycle counts disagree.
The part that is not a lock
Here is the thing the product pages do not sell you. When a door is forced, the bolt is usually not the part that gives. The frame is. A deadbolt throws into a strike plate that, on most builder installed doors, is held by short screws seated in the jamb trim rather than the structural framing behind it. Load the door and the wood around the strike splits.
That is a mechanical description, not a statistic, and this site does not publish burglary percentages it cannot trace to a primary source. The fix that locksmiths routinely recommend is replacing those short screws with 3 in. screws long enough to reach the framing behind the jamb; ACME Locksmith's reinforcement guide describes exactly that, read 23 August 2026. A reinforced strike plate with a larger footprint spreads the load further.
No lock, and no rating on any lock, makes a door impossible to force. A grade tells you how a sample performed in a laboratory test. It is not a promise about your doorway. Two guides in this cluster go deeper: one on strike screws, one on reinforcement.
The five types of door locks side by side
| Type | What it does | Security role | Typical US door |
|---|---|---|---|
| Deadbolt | Throws a solid bolt into the frame by key or thumbturn | The primary resistance on the door | Any exterior door, mounted above the knob |
| Keyed knob or lever | Spring latch with a key cylinder in the handle | Access control, not force resistance | Exterior door as a secondary, or interior keyed door |
| Handleset | Deadbolt plus a latch behind one exterior plate | Same as the deadbolt inside it | Front entry doors, appearance driven |
| Mortise lock | Latch and deadbolt in one case inside a pocket in the door edge | Combined, varies by case | Older homes, heavier or commercial style doors |
| Smart lock | A deadbolt or thumbturn driven electronically as well as by key | Same as the deadbolt it is or drives | Any door within the maker's thickness and backset range |
How to choose, by situation
| Your situation | Where to start |
|---|---|
| Front door has a keyed knob and no deadbolt | Add a deadbolt. That is the upgrade, not a better knob. |
| Front door has a knob and a deadbolt already | Check the grade and the strike screws before replacing anything. |
| Glass sidelight or glazed panel next to the door | Read the cylinder guide before considering a double cylinder, and ask your building department. |
| You rent, or you want to keep your existing key | A retrofit smart lock leaves the exterior cylinder alone. |
| Old house, rectangular pocket in the door edge | You have a mortise lock. Measure the case before shopping. |
| Steel or fiberglass door, or a thick slab | Check the maker's door thickness range first. Some locks will not span it. |
| Bedroom or bathroom | Privacy function. Not a security purchase. |
FAQ
Do I need a Grade 1 deadbolt on a house?
Usually not. Grade 1 is the highest performance level in the ANSI/BHMA numeric system, and it is aimed at heavier duty applications. For most homes a Grade 2 deadbolt installed in a reinforced strike with long screws is the sensible default, because the frame around the bolt is more often the limiting part than the bolt itself.
Is a keyed knob enough on a front door?
No, not on its own. A keyed knob uses an angled spring latch, the same mechanism that lets the door click shut when you push it, so it is designed to yield under pressure. It controls casual access. If your exterior door has only a keyed knob, adding a deadbolt is the meaningful upgrade.
Can I put a smart lock on any door?
No. A smart lock has the same fit constraints as any deadbolt: the cross bore diameter, the backset, and above all the door thickness range printed in the maker's specification. Thick doors, unusual backsets and mortise prepared doors all rule out large parts of the market. Check the spec sheet, not the marketing copy, before ordering.
What is a mortise lock?
A mortise lock is a lock case containing both a latch and a deadbolt that slides into a deep rectangular pocket cut into the edge of the door, rather than into two round bored holes. It is common in older US homes and heavier doors. Cases are not interchangeable between brands, so identification and measurement come before shopping.
Do I need a double cylinder deadbolt if there is glass beside the door?
Not necessarily, and it is not purely a security question. A double cylinder needs a key on the inside, and IRC Section R311.2 requires an egress door to be readily openable from inside without a key or special knowledge or effort. Jurisdictions apply that differently. Ask your local building department before you buy one, and consider glazing and frame options as alternatives.
How this guide was researched
Door preparation dimensions are quoted from Schlage's published door preparation checklist. Grade descriptions come from the Builders Hardware Manufacturers Association's own pages for the ANSI/BHMA A156.39 and A156.40 standards and from Schlage's consumer page on BHMA residential security grades. The egress language is quoted from Section R311.2 of the International Residential Code. The strike screw recommendation is attributed to ACME Locksmith's door reinforcement guide. All read 23 August 2026. Brands are named as examples of a category, not as recommendations. No product on this page was tested by this site, and this page contains no burglary statistics, because the widely repeated figures we found could not be traced to a primary source.