How to Open a Master Lock Key Box: Easy & Secure Steps
Published: Dec 15, 2025
It usually happens at the worst time. You’re on the porch after a long day, or your Airbnb guests are texting from the steps, and the only way in is the spare key locked inside a Master Lock key box that suddenly won’t open. In moments like these, you don’t want to guess, force the box, or risk damaging it — you just want the key in your hand.
In most cases, opening a Master Lock key box is still as simple as sliding the cover down, lining up the dials to the exact code, and pressing the release while pulling the door toward you. This guide from Sure Lock & Key shows you how to open a Master Lock key box using the code, plus what to try if it’s stuck, so you can reach that spare key without harming the box or your door.
How to Open a Master Lock Key Box with a Code in 4 Simple Steps
Once you’re standing at the door with the code in your head and the box in front of you, you just need it to work. If you’re using a standard dial-style model and wondering how to open a Master Lock key box with a code, the process is usually simple as long as the box is in good shape.
Step 1: Reveal the dials
Pull the black weather cover down. This plastic shield protects the dials and internal parts from rain, ice, and road dust.
Step 2: Align the combination
Rotate the four dials until your code lines up exactly with the center guideline. Even a half-click off can keep the latch from releasing.
Step 3: Engage the mechanism
Press the black release button or pull down the “OPEN” lever on the left side of the dials. You should feel the latch release when everything is lined up correctly.
Step 4: Open the compartment
While holding the lever or button, pull the door toward you to access the key compartment.
If you’re not sure which model you have, our guide on what an outdoor key box is can help you see whether you’re using a standard dial version or a push-button style. After you’ve taken the key out, always close the compartment and scramble the dials right away to keep your code private and your lock box secure.
Master Lock Key Box Won’t Open? 3 Simple Fixes to Try
Sometimes a Master Lock key box won’t open even when you’re sure you’ve entered the right code. That doesn’t always mean the box is ruined — often it’s just latch pressure, dirt in the mechanism, or parts that have stiffened after sitting outside for months. Springs can get sticky, and the door can cling to the gasket from heat or moisture.
Fix 1: Relieve latch pressure
Press the door firmly inward toward the box while you enter your code. This takes pressure off the locking dog (the internal latch) and often gives the release lever enough room to move freely.
Fix 2: Clear debris from the dials
If the dials feel gritty or hard to turn, dust or rust may be keeping them from settling into the correct positions. A quick blast of compressed air around the dials and release area can help clear the mechanism
Fix 3: Gently jiggle the lever
Sometimes the release fork (the part that moves the latch) catches on one of the internal wheels. With your code set, gently wiggle the black lever side to side while applying steady downward pressure to help it slide past any rough spots.
If the box stays jammed after these steps, don’t force it with a pry bar — that can damage the wall, frame, or mounting surface. At that point, calling a professional residential locksmith is the safest option. Sure Lock & Key can remove a failed box, help you get to your keys, and install a new unit without harming your property.
How to Open a Master Lock Key Box When You Forgot the Combination
If you’re wondering how to open a Master Lock key box when you’ve forgotten the combination, you have three safe options to consider.
Method 1: Gentle testing
Use only light pressure. Apply gentle tension to the release button or lever while slowly turning each dial. If you feel a small change in resistance on a number, that may be the correct position. Don’t force anything — too much pressure can damage the internal wheels.
Method 2: Check paperwork and registration
Look through any original instructions, packaging, or registration emails for the stored code or recovery steps. Our guide on unlock a Master Lock without a key explains common manufacturer-approved options and what information you may need to provide.
Method 3: Manufacturer or locksmith help
If the manufacturer can’t recover or reset your combination and the box still won’t open, avoid cutting or prying it off the door yourself. Sure Lock & Key can safely remove the lock box, help you get to your keys, and install a new unit with a fresh, documented combination.
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Ready to Get Back Inside?
If you’re still wondering, “How do you open a Master Lock key box?” it really comes down to three situations: the code is right and the box should open, the mechanism is stuck, or the combination is gone for good. When everything is working, the right code and a press of the release should open it. If it’s stuck, a bit of latch pressure and a quick clean around the dials can help. If you can’t remember the combo at all, your best bet is manufacturer recovery or professional removal.
If you’re tired of guessing at the problem or don’t want to risk scratching the door or siding, Sure Lock & Key can take it from here — helping you get back to your keys and setting up a new lock box so the next time you need that spare, it actually works.
Frequently Asked Questions
How to unlock a Master Lock key box if it’s working normally?
If the box is in good shape and you know the code, slide the cover down, line up the dials with your numbers, press the release or lever, and pull the door toward you to open the compartment.
Why won’t my Master Lock box open with the code if I’m sure it’s correct?
If the right numbers don’t work, the latch may be under pressure, the dials may be dirty, or the internal parts may be worn. Try pressing the door inward while entering the code and gently working the lever. If it still won’t open, it’s time for professional help.
When should I do a lock box reset?
You should change the code any time a guest, tenant, contractor, or former roommate no longer needs access. Always reset with the door open, choose a new code you can remember, and test it a few times before closing the box.
How to open a Master Lock 4-digit combination safely the first time?
Use good lighting, set all dials to the default or current code, then press the release while pulling the shackle or door. Go slowly so you feel how the mechanism works instead of forcing it.
Is there a safe way for how to open a Master Lock key box without a code?
There’s no simple, legitimate shortcut to bypass the combination. Check any paperwork or registration for the original numbers, contact the manufacturer for recovery options, or call a locksmith to remove the box without damaging your door or wall.