How To Replace a Mailbox Lock in Under Five Minutes


Replacing a Mailbox lock is simple even if you’ve never done it before and/or can’t get into it. Let’s review the process with images to guide us.

Recently I moved into an older home and found the mailbox key had issues opening the lock. After a few weeks, the mailbox key refused to open it. Great! No matter what I tried (graphite powder and spray included), after a few days of not being able to get my mail, I knew it was time to replace the lock.

Although we frequently focus on Technology, I love handy DIY tricks, so I thought I’d share this little adventure I had a few days ago.

I started the adventure by calling my local post office, and that was a waste of time. They suggested a local locksmith and hung up on me. Yelp pointed me at a local locksmith who quoted me $250 for an onsite replacement plus an additional $150 an hour after 30 minutes.

So yeah, you can guess the path we’re going to take on this one. Time to get medieval on the mailbox lock!

Thankfully I have a cordless drill, so I grabbed a bit that fit nicely into the key hole of the lock. The primary goal here is not damaging the housing holding the lock so don’t use a lot of pressure when drilling into the lock. Just drill straight and apply consistent pressure.

Note: If you’re not the adventurer / handy type or if you don’t have a drill, wait for your mail carrier. They will have access to the back of the mailbox, and you can perform the steps below from inside the box. It’s not nearly as fun, but that is another option.


Once you drill through the entire lock mechanism, the mailbox door should open easily.


Slide the lock bar and metal clip holding the lock mechanism against the door. In some cases, the lock nut may still be attached to the lock. Use a wrench to take off the nut (although, in my case, the drill took care of that for me).


Without the clip holding the lock in place, popup the entire mechanism and bring it to a local locksmith. In my case, although my original lock was 15-years-old, he had an exact match that cost me just $12. If you’re not able to find a local locksmith, however (or don’t have time), just grab a replacement mailbox lock from Amazon. The National Mailbox Lock C9100 should do the trick for a clockwise rotation or the C9200 for counterclockwise.

Note: If you’re an HOA or Apartment complex and need more than one lock, here’s a link for the C9100 lock or C9200 in bulk.


Once you have the new lock, slide it into the lock housing the reattach it in a locked configuration (lock bar out).


Screw on the nut and you’re done!


The new mailbox lock I purchased was a bit sticky. I solved this with a little Graphite Powder. Amazon has it listed for ~$5 however I found it at a local HW store for under $2 the next day.


In all, the entire job took no longer than 5 minutes (not counting the trip to the locksmith). Not bad considering the quote from the locksmith $250. I’ve always enjoyed DIY projects especially the ones with a drill involved. It’s an excellent bonding opportunity for my son and me, and a good way to show with a little work, almost any job is possible with a little time and patience.

Is it Legal to fix your Mailbox Lock?

Since publishing the DIY mailbox lock fix, several readers have expressed concern about the legal aspects of fixing your mailbox lock yourself. Although I can’t give legal advice, I did find a page on regarding mailbox maintenance. Along with a guide on how to install a new mailbox, it also provides guidance on maintenance.

USPS.COM: Mailbox Maintenance

Mailboxes take a beating from the weather, so we recommend an annual mailbox checkup to avoid damage to your mail or difficulty identifying your address.

  • Tighten loose hinges on the door
  • Take care of rusty or loose parts
  • Replace missing or faded house numbers
  • Keep the path to your mailbox clear

Based on this information directly from the United States Postal Service, it’s clear that the responsibility for maintenance and care of the mailbox falls on the property owner/manager.

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