A double cylinder deadbolt requires a key on both sides of the door, so it locks and unlocks from the exterior and the interior only with a key — never a thumbturn.
Break the glass beside a standard deadbolt and a stranger can simply reach in, twist the thumbturn, and walk through. That single weakness is the reason double cylinder deadbolts exist. The lock removes the interior thumbturn entirely and replaces it with a second keyed cylinder, so a smashed pane no longer gives anyone an easy way to open the door.
The trade runs the other way, though. Everyone inside the house now needs a key to get out, and that changes how you handle emergency exits. Here is how the mechanism works, who it suits, and what to sort out before you buy.
What Makes a Double Cylinder Deadbolt Different?
A double cylinder deadbolt uses two keyed cylinders — one on the outside face of the door, one on the inside face — while a standard single cylinder deadbolt pairs an exterior key cylinder with an interior thumbturn.
Schlage describes its B62 double cylinder deadbolt as “perfect for use on entry doors with glass needing an additional layer of security,” and states plainly that a key is required to lock and unlock it from both the exterior and interior. That is the whole design in one sentence: no key, no movement, from either side.
Mechanically, both versions share the same bolt, strike plate, and strike pocket. The difference sits in the trim. Turn the key in the outside cylinder and the bolt throws or retracts. Step inside, and you repeat the same motion with a key in the interior housing. There is no lever, no knob, and no thumbturn to grab.
That absence is the point. A thumbturn is a convenience feature that only works when the person turning it is authorized to be there — and broken glass does not check credentials.
Where A Double Cylinder Deadbolt Actually Belongs
These locks make sense on doors that have glass within arm’s reach of the lock: a full-lite entry door, a door beside a sidelight, or any entry where a window panel sits close enough that a hand could reach through the opening.
On those doors, a single cylinder deadbolt has a known vulnerability. An intruder breaks the glass, reaches inside, and unlocks the door in seconds. A double cylinder deadbolt closes that route because the reaching hand finds a keyway instead of a thumbturn.
- Good fit: entry doors with glass panels, sidelights, or adjacent windows near the lock.
- Poor fit: the main door a household uses to leave during a fire or emergency.
- Common setup: a double cylinder deadbolt on a glass-adjacent entry, paired with a single cylinder deadbolt on the primary exit door.
Grade matters too. Kwikset’s 985 and Schlage’s B62 are both Grade 1 options, the top residential rating for bolt strength and cycle testing. Finishes vary widely across both lines, from satin chrome to matte black.
The Safety Question You Have To Answer First
The interior key requirement is the lock’s biggest drawback, because exiting during a fire or a medical emergency now depends on finding and turning a key in the dark.
Building codes in many US jurisdictions restrict or prohibit double cylinder deadbolts on egress doors for exactly this reason, and rules differ by state and municipality. Before installing one on any door that serves as a way out, confirm what your local code allows and check with your local building department.
If you do install one, the practical mitigations are simple and worth doing the same day: keep a key in the lock or on a hook within reach of the door, and place a second key somewhere every adult in the house knows about. Never leave the interior side keyless for convenience and never store the key so far away that it defeats the purpose.
For households with small children, older adults, or anyone who might struggle under pressure, a single cylinder deadbolt on the main exit is usually the wiser choice.
What To Check Before You Buy
Double cylinder deadbolts are not one-size-fits-all, and buying on finish or model name alone is the most common mistake.
A Schlage satin chrome double cylinder deadbolt, for instance, is listed with an adjustable backset, which covers the two common door-prep measurements. Even so, verify these before ordering:
- Backset: the distance from the door edge to the center of the bore hole, typically 2-3/8 or 2-3/4 inches. Adjustable models cover both.
- Door thickness: standard is 1-3/8 to 1-3/4 inches. Thicker doors need longer bolts or a different kit.
- Cross bore and door prep: confirm your door is already drilled for a deadbolt, or plan to bore it.
- Handing and strike: check the strike plate size and the door swing against the model’s spec sheet.
If you would rather compare tested options side by side before committing, our roundup of the best double cylinder deadbolt picks breaks down finishes, grades, and backset options. Schlage’s B62FFF product page lists the full specs for that line.
| Consideration | Single Cylinder Deadbolt | Double Cylinder Deadbolt |
|---|---|---|
| Interior operation | Thumbturn, no key needed | Key required to lock and unlock |
| Glass-adjacent doors | Vulnerable after glass breakage | Resists reach-in entry |
| Emergency egress | Fast, no key needed | Slower, key required |
| Typical code status | Generally permitted | Restricted on some egress doors |
| Best use | Primary exit doors | Entry doors with nearby glass |
| Grade options | Grade 1 through Grade 3 | Grade 1 models available |
| Kids and older adults | Easy to operate | Can be difficult under stress |
The Bottom Line On Double Cylinder Deadbolts
A double cylinder deadbolt trades everyday convenience for resistance to glass-break entry, and that trade only pays off on the right door. Put one on a glass-adjacent entry and it does real work. Put one on your main exit and you have created a hazard.
Before you buy, confirm three things: the door’s backset and thickness, what your local code says about egress, and where the interior key will live so it is always within reach. Get those settled, and the lock does exactly what it was designed to do.
FAQs
Can a double cylinder deadbolt be rekeyed?
Yes. Both cylinders on a double cylinder deadbolt can be rekeyed, and a locksmith can usually key them to match your other entry locks so one key opens everything. Some Kwikset models support homeowner rekeying with a SmartKey kit, which lets you reset the lock yourself without removing it from the door.
Is a double cylinder deadbolt the same as a double keyed deadbolt?
Yes. “Double keyed” is simply another name for the same lock. Both terms describe a deadbolt that requires a key on the exterior and interior sides, as opposed to a single cylinder deadbolt that uses a thumbturn inside. Retail listings use the two names interchangeably, so compare specs rather than labels.
Do I need a double cylinder deadbolt on every exterior door?
No. Most homes only benefit from one on doors with glass near the lock. Standard solid entry doors are already protected by a single cylinder deadbolt with a thumbturn, which is faster to exit in an emergency and generally allowed on egress doors under local building codes. Reserve the double cylinder for the glass-adjacent door.
References & Sources
- Schlage. “B62FFF Double Cylinder Deadbolt” Confirms a key is required to lock and unlock from both sides, and lists backset, material, and finish specs.
- idighardware.com. “Decoded: Key-Operated Locking Devices” Explains how key-operated locking devices function and the egress and code questions tied to double cylinder deadbolts.
- Gardening Beyond. “Best Double Cylinder Deadbolt” Our tested roundup of current double cylinder deadbolt models, grades, and finishes.