One Key for Front and Back Doors: What to Settle First

Front and back door locks can usually be set to use one key, either by rekeying one or both cylinders or by replacing one or both locks. Which route works depends on what lock is on each door now and whether their keyholes accept the same key shape. Before choosing a method, settle who needs access to both doors and how many keys you want in circulation.

Keyed alike starts with a few choices

Keyed alike means two or more locks open with the same key. Each keyed lock has a cylinder, the part with the keyhole, which holds small pins set to different heights. A key works when its cuts line those pins up. Two locks share a key when their pins are set to the same pattern and their keyholes accept the same key blank.

That gives the plan its order. Find out what each lock is first. Then decide who should open both doors. The method and the number of keys follow from those answers.

What to look at on each door

Matching depends on each lock's cylinder, not on the door. A wood front door and a metal back door can share a key if their cylinders can be set alike. You can do most of this inventory just by looking.

• Keyholes per door. A deadbolt plus a keyed knob or handle set means two cylinders on that door, and both need to match for one key to open everything.
• Keyhole shape. Hold the two keys side by side. If the grooves along the blades differ, or one key won't slide into the other door's lock, the keyways differ. A keyway is the profile of the slot, and a key has to fit it before its cuts matter. Don't force a key that resists.
• Condition. A smooth turn and a bolt that slides fully out suggest a lock worth keeping. Sticking or a loose cylinder points toward repair or replacement first.
• Electronic locks. Many keypad and smart locks keep a key cylinder as a backup, and that cylinder belongs in the count.

Locks from different makers often use different keyways. When the keyways don't match, one cylinder or one lock usually has to change. When they do match, rekeying alone is often enough.

Four decisions, in order

Who should open both doors

One key for two doors is convenient, and the tradeoff is direct: a key that opens the back door also opens the front. In a household where everyone uses both entrances, that changes little. It matters when access is uneven, such as a tenant and a property manager, or a shop where staff use the back door and only the owner should open the front. If someone needs one door and not the other, keep that door on its own key or consider a keypad there.

Keep and rekey, or replace

Rekeying means changing the pins inside a cylinder so it works with a different key, while the lock stays on the door. If both locks are sound and share a keyway, rekeying is usually the simpler route. Replacement comes up when the keyways don't match, a lock is worn, or you want a stronger lock on one door. A high-security lock often uses a keyway ordinary keys won't enter, so matching it means fitting a compatible cylinder on the other door.

Match the old key or start fresh

Setting the back lock to your current front key keeps the keys you carry working. It also means every old front key, including copies you've lost track of, now opens the back door. If keys are missing or still with past occupants, putting both locks on a new key closes that gap.

How many keys to make

Count people, not doors. List each person who needs a key, add one spare kept off your own ring, and stop there. Each copy is another way into both doors. If one lock is coming off anyway, it's a reasonable time to look at a security upgrade on that door, as long as that choice doesn't hold up the matching.

What to have ready when you call

A short list makes the first conversation with a locksmith easier:

• The number of doors and how many keyed locks are on each
• What each lock is now: deadbolt, knob, lever handle set, or electronic lock with a key backup
• Which locks you want to keep and which you'd replace
• Whether each current key fits the other door's keyhole
• How many keys you want and who will hold them
• Any keys that are lost or still with former occupants, staff, or contractors

That last item often settles the method, because outstanding keys are a strong reason to move both doors to a new key. Amsterdam Locksmith handles lock changes and rekeying for homes and businesses on the Upper West Side and elsewhere in Manhattan. With your list ready, call (917) 200-2978 to talk it through.

Frequently asked questions

Does keying two locks alike make them less secure than keeping them separate?

Keying two locks alike leaves each lock's mechanism as it was. What changes is access: one key opens both doors. If that shared key goes missing, both cylinders need rekeying, not just one. For a household that uses both doors, that is usually an easy trade for carrying a single key.

Can a keyed-alike setup be changed later if one door needs different access?

A keyed-alike setup can be changed later. Either cylinder can be rekeyed to a new key on its own, which leaves the other door on the shared key. The person who should open only one door then gets a key for that door alone. Noting which locks were matched makes that later change simpler to plan.

What if my front and back door locks are different types, such as a deadbolt and a handle set?

A deadbolt and a handle set can share one key if each has a keyed cylinder that accepts the same key blank. The type of lock matters less than the cylinder inside it. If the keyways differ, one cylinder or lock usually needs replacing. A handle set with no outside keyhole has nothing to match.

Should a rental or shared property keep separate keys for each door?

A rental or shared property can go either way. One shared key makes turnover simpler: when an occupant leaves, rekeying moves both doors to a new key in one step. Separate keys suit a property where someone, such as a cleaner or property manager, needs only one entrance and should not carry a key to the other.