What a deadbolt does that a handle lock does not
A standard knob or lever lock holds the door closed with a spring latch, the angled piece that slides back when you turn the handle. A spring latch is convenient but is not designed to resist force. A deadbolt uses a solid bolt that is thrown by turning a key or a thumbturn, and it stays in place until someone turns it back. It does not retract by pressure, which is why it is called dead.
The result is that a properly fitted deadbolt gives noticeably more resistance than a latch alone. That resistance depends on the length of the bolt that enters the frame, the strength of the strike plate and the screws that hold it, and the quality of the door and frame. A deadbolt in a weak frame is a bolt that can be torn out of the wood.
Most exterior hinged doors benefit from having both: a handle set for daily convenience and a deadbolt for real resistance. The type of deadbolt you choose depends on how the door is used, what is near it and who lives in the home. This page compares the common types so you can ask for what fits.
Single cylinder deadbolts
A single cylinder deadbolt has a keyhole on the outside and a thumbturn on the inside. You unlock it from outside with a key and from inside by turning the thumb piece. This is the most common type in homes and is the default recommendation for most exterior doors.
Its main advantage is that anyone inside can leave quickly without searching for a key. In a fire, a medical emergency or any other situation where seconds count, a thumbturn is the fastest way out. Fire safety professionals generally prefer thumbturns on exit doors for this reason, and many building rules require some form of quick release on doors used for exit.
The weakness is that the thumbturn can be reached if there is glass or a thin panel near it. A person who breaks the glass can reach in and turn it. That does not make single cylinder locks poor choices. It means you should look at what is near the lock, and consider other measures such as laminated glass, security film or moving the hardware if glass is within arm's reach.
Double cylinder deadbolts
A double cylinder deadbolt has a keyhole on both sides. You need a key to lock or unlock it from inside as well as outside. It is sometimes chosen for doors with glass nearby, because breaking the glass and reaching in no longer helps without the key.
The tradeoff is serious. In an emergency, anyone inside needs a key to get out. If the key is not in the lock or immediately at hand, that delay can be dangerous. A fire, a medical event, a child alone in the home or a person with limited mobility all raise the risk. Many fire safety guidelines and some building rules discourage or prohibit double cylinder locks on exit doors, and some insurers and property managers have their own preferences.
If a double cylinder lock is used, it is typically paired with a firm household rule about where the key is kept, such as on a hook near the door and out of reach from the glass. This is an area where we strongly suggest speaking to a technician about the door, glass and household before choosing, and checking any rules that apply to your building or association.
Thumbturn-only and keyless deadbolts
A thumbturn-only deadbolt has no keyhole on the outside. It is operated from inside, and it is used on doors that are not meant to be opened from the outside at all, such as a secondary door that is always accessed from within or a patio door that should only be opened from the home. This removes the keyway as a point of attack and removes the need for a key.
The limitation is obvious: if you leave through that door and lock it behind you, you cannot unlock it from the outside. It suits doors you do not use to enter, such as a back door that you only open from within, and you need another way in. It is not a choice for a main entry.
Keypad and smart deadbolts are a related category with no external keyhole or with a hidden backup keyway. They add electronic features and dependencies, and they are covered in more detail in the smart lock guide and on our page about keypad lock setup.
Where each type fits in a Miami-Dade home
Single cylinder deadbolts suit most front doors, garage entry doors and side doors on single-family homes, townhouses and condos. They allow quick exit and are generally accepted by building managers. For a house with solid doors and no glass near the lock, a quality single cylinder deadbolt is the standard choice.
Doors with sidelights, glass panels or transoms may need extra thought. Consider laminated or impact-rated glass, security film or relocating the lock. Where a double cylinder is considered, think carefully about who lives in the home and how a quick exit would work. Families with small children, older residents and people with mobility challenges are all reasons to lean towards a thumbturn.
In high-rise condos, many associations specify the hardware on the unit door and may require that the building holds a key. Others restrict certain lock types. Check the rules before you buy or ask for work, and read the condo door hardware rules page. Rental properties and short-term rentals may have their own rules, particularly where guests unfamiliar with a door need to leave quickly.
The bolt, the strike plate and the frame
Whichever type you choose, the parts around it matter. A bolt that extends a good distance into a solid frame resists more than a short bolt in a soft one. The strike plate, the metal piece set into the frame where the bolt enters, should be anchored with screws long enough to reach the framing behind the jamb, not just the thin trim.
Over time, doors in South Florida can swell and shrink with humidity, and frames can soften from moisture or insects. If a deadbolt has become hard to throw, if you have to lift or push the door to lock it, or if the bolt does not fully extend, the problem is often alignment between the bolt and the strike plate, not the lock itself. Adjusting or replacing the strike plate can fix this.
Our page on door reinforcement and strike plates explains how the frame side is strengthened, and door frame repair for lock fit covers cases where the frame has been damaged.
Cylinder quality, keyways and rekeying
Inside every deadbolt is a cylinder that reads the key. Quality cylinders are made to closer tolerances, resist wear better and may use a more complex keyway that is harder to copy. A deadbolt that has been in use for many years can develop wear that makes it stiff, makes the key stick or allows the bolt to move unexpectedly.
Many deadbolts can be rekeyed, which means changing the internal pins so that old keys no longer work and new ones do. This is useful when you move into a new home, after a breakup, after keys are lost or when a person who held a key no longer should have it. It is usually less involved than replacing the lock, and it can often be done on site. See rekey or replace: which is right for guidance on choosing.
If you want several doors to share one key, a technician can rekey them to match. That reduces the keys you need to carry while still allowing a lock on each door. We do not describe how to open locks without keys, and the rekeying work should be done by a professional so that the lock works properly afterward.
Safety tradeoffs in plain terms
Every choice here balances two risks: someone getting in who should not, and someone being unable to get out when they need to. A thumbturn favors quick exit. A double cylinder favors resistance to reach-in attacks. Neither is right for every door, and the safest approach depends on the household and the layout.
A practical test is to imagine a fire at night. Could every person in the home, including children, older relatives and guests, find and open the nearest exit door in the dark within seconds? If the answer is not a clear yes for a door fitted with a double cylinder, reconsider.
If glass near a thumbturn is the concern, solve the glass problem rather than the lock problem where you can. Laminated glass, security film or a different door can address the exposure without taking away the quick exit. A technician can look at your door and advise, and they will not suggest anything that compromises the household's ability to leave in an emergency.
- Can everyone in the home open the exit door quickly without a key?
- Is there glass within arm's reach of the thumbturn?
- Does the building or association restrict lock types?
- Where will the key be kept if a double cylinder is used?
- Does anyone in the home have limited mobility or a risk of confusion?
Example situations and what tends to fit
A family in a Kendall single-story house with a solid front door and no glass nearby is a straightforward case. A single cylinder deadbolt in a durable grade, with a strike plate anchored into the framing, covers the need. The main decision is the finish and whether to key the front and garage entry doors alike so one key serves both.
A Coral Gables home with a wide entry, arched decorative glass and a sidelight beside the handle is a different case. Here the thumbturn may sit close to glass, so the conversation turns to laminated glass, film or a different placement, with a double cylinder as a last option only if the household can manage the emergency-exit risk. An older couple or a household with young children would likely rule that option out.
A Miami Beach condo with a unit door that the association keys to a building system is limited by rules more than by taste. The technician's job is to work within the approved hardware, confirm that the deadbolt throws fully and make sure the door closes and latches properly on its own. A rental unit used by short-term guests leans towards simple, familiar hardware that guests can operate easily, because confusion at a door is a safety risk too.
Getting a deadbolt installed or replaced
When you call, tell the technician which door it is, what is on it now, any problems you have noticed, whether there is glass nearby and who lives in the home. They will ask about the door's thickness and material, and they may ask for photos to understand the setup. Quotes are given by phone, and more complicated installations may need an on-site look first.
A professional installation includes checking that the door is in good condition, that the bolt aligns cleanly with the strike plate and that the lock is operated several times to confirm it works smoothly. Keys should be tested, and you should receive all copies. If any part of the door or frame is damaged, the technician will tell you and explain the options.
A service call charge applies and is explained on the phone before dispatch. For the sequence of events, read how a locksmith call works. When you are ready to choose a deadbolt for a door, call and we will talk through the right type for your home.
Questions people ask
Which deadbolt type is best for a front door?
For most front doors, a single cylinder deadbolt with a thumbturn inside is the standard choice because it allows quick exit and is widely accepted. If there is glass near the lock, consider laminated or impact-rated glass or film first. Where a double cylinder is being considered, think carefully about emergency exit and building rules.
Is a double cylinder deadbolt legal to use at home?
Rules vary by building, association and local requirements, and some restrict or prohibit double cylinder locks on exit doors for safety reasons. Check with your association, landlord or local authority before installing one. A technician can also tell you what is commonly accepted, but they cannot replace checking the rules that apply to your property.
Do I need a deadbolt if my handle already locks?
A handle lock is usually a spring latch, which resists force less than a deadbolt. Most exterior doors benefit from both. A deadbolt adds a solid bolt that stays thrown until turned back. If your front door has only a knob lock, adding a deadbolt is one of the most common upgrades.
Can a deadbolt be rekeyed so my old keys stop working?
Many can. Rekeying changes the pins inside the cylinder so that existing keys no longer work and new keys do. It is common after a move, a breakup or a lost key. Some locks are not worth rekeying if they are worn, and a technician can advise whether to rekey or replace.
What if my deadbolt is hard to turn?
Often the cause is misalignment between the bolt and the strike plate, caused by a door that has swelled or shifted, or a worn cylinder. Do not force it, since a stuck bolt can break inside the lock. A technician can check the alignment, adjust the strike plate or replace the lock if needed. Call and describe when it happens.
Are keypad deadbolts the same as regular ones?
They use the same basic bolt concept but add electronics for entering a PIN or using an app. That adds convenience and also dependencies such as batteries. Many have a backup key. Their security depends on both the mechanical build and how the electronics and access are managed, which is covered in our smart lock guide.
Describe the situation by phone and we will tell you what the job involves. Quotes are given by phone. Jobs that cannot be quoted without seeing them need a technician on site, and the service call charge is explained on the phone before anyone is dispatched.
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Written by Claude (AI) (AI) for 24 Hour Locksmith Miami.