Dad lost a house key. Or he cannot remember who has copies. He wants the house secure, but he does not want a locksmith turning one missing key into a renovation.
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Fair position.
The first decision is not which lock to buy. It is whether the existing locks can be rekeyed. Rekeying changes the pins or internal parts so the old key no longer works. Replacing changes the lock hardware itself. If the hardware is sound and the goal is simply to cancel a missing key, rekeying is usually the narrower job.
The expensive sentence is, “While you are here, replace everything.” Do not say that until someone has counted what “everything” means.
The legal line comes before the screwdriver
Dad owning the house does not make his adult son an owner, contractor or security manager. Having an old key does not supply authority either. If Dad owns and occupies the house, get his clear permission before ordering work. Put the agreed scope in a text or short note so nobody has to reconstruct the conversation later.
If the property has another owner, tenant or lawful occupant, do not change locks in a way that excludes that person. Missouri law treats a landlord's removal or exclusion of a tenant without judicial process and a court order as forcible entry and detainer (Missouri Revised Statutes, section 441.233). A family disagreement does not create a locksmith exception.
If Dad rents, check the lease and call the landlord or property manager before touching the hardware. Ask who must arrange the work, who receives the new keys and whether a particular lock format is required. If ownership, tenancy or your authority is disputed, stop. The practical route is Missouri legal help, not a faster drill bit. The site's Local Help in St. Louis page gives a place to start.
What actually drives the bill
How many keyed cylinders are involved. Count cylinders, not doors. A front door may have a keyed knob and a separate deadbolt. A storm door may add another. The back door, basement walkout, detached garage and side entry can turn “the front lock” into a much larger job.
Whether the locks can be rekeyed. Ask the locksmith to identify which cylinders are serviceable before approving replacement. Worn, damaged, corroded or incompatible hardware may need replacement. Cosmetic dislike does not.
Whether one key should operate several doors. Keying compatible locks alike can reduce the number of keys Dad carries. It may also require changes to several cylinders. Ask which existing locks are compatible and which are not. “One key for everything” sounds simple until the garage uses a different system.
The condition of the door. A lock cannot cure a sagging door, split frame or misaligned strike plate. If the bolt rubs, Dad may blame the new lock and stop using it. Ask whether the quoted work includes adjustment of the strike, tightening hinges or repairing the frame. Those are separate labor and material decisions.
The service call. The trip, arrival window and urgency may be separate parts of the charge. Ask whether the quote changes outside normal service hours and whether waiting for a scheduled visit reduces the total. If the missing key can be tied to Dad's address and there is a credible entry risk, urgency may be worth paying for. If the key is probably under a recliner, urgency is a different calculation.
Electronic features. A keypad or connected lock adds hardware, setup and future battery or account management. It can help if Dad loses keys but remembers a code. It can also create a new failure point if he dislikes codes, phones or warning beeps. Do not pay for remote access until Dad has tried the actual entry routine and agreed to use it.
Extra copies and restricted key systems. Decide how many authorized people need a key before the locksmith arrives. Ask what a replacement copy requires and whether ordinary hardware stores can duplicate it. Tighter control over copying may raise the cost and make later copies less convenient.
Unknown hardware. Clear photos of both sides of every lock, the edge of each open door and the full door can prevent a vague telephone quote. Include the brand marking if visible, but compare scope rather than brand promises.
Ask for the same quote from each locksmith
A cheap quote for one cylinder cannot be compared with a quote covering five cylinders, door adjustment and new hardware. Give each company the same facts and ask for a written estimate that separates:
• Service call and labor
• Number of cylinders to rekey
• Number of locks to replace
• Hardware included
• Door or strike adjustment
• Number of new keys
• Charges that could be added after arrival
• Warranty on labor and hardware
The Federal Trade Commission recommends getting multiple written estimates and making sure the description of work, materials and price are stated before work begins (Federal Trade Commission, How to Avoid a Home Improvement Scam). That is ordinary household defense, not distrust.
Ask one final question: “What would make this price change once you see the doors?” A useful answer names specific conditions. An answer consisting mostly of throat clearing is also information.
The side door Dad may accept
Do not lead with burglary, decline or the possibility that he will lose another key. Lead with cancellation.
“The old key should stop working. We can rekey the exterior locks and keep the hardware you already know.”
That offer protects Dad's control. He chooses which doors are included and who receives copies. You are solving the missing-key problem, not using it to redesign his house.
If he refuses the full job, ask about one smaller move: rekey the door connected to the missing key, verify that the other doors latch properly and make a written list of authorized keyholders. A limited job completed with consent beats a comprehensive job that starts a family war.
When this is not really a lock job
If Dad is locked outside, check for immediate hazards before shopping. If he is injured, exposed to dangerous weather or cannot safely wait, call emergency services. A locksmith opens a door. A locksmith does not assess an injury.
If someone may already be inside, or there are signs of forced entry, do not enter to investigate. Call law enforcement from a safe place.
If keys keep disappearing, changing the locks after every episode treats the evidence, not the pattern. Record where keys are normally kept, who receives copies and when a copy is returned. Consider a fixed key routine that Dad approves. The point is to make the next missing key understandable, not to turn the house into a checkpoint.
For the source trail behind the legal and consumer boundaries used here, see Sources.
Your next move
Tonight, photograph every exterior lock and write down three things: who owns or rents the property, how many keyed cylinders exist and which old keys must stop working. Then ask Dad one clean question: “Do you want the narrow rekey job, or do you want quotes for replacement too?” His answer is the scope. Use that same scope to request written estimates.