Mailbox locks are essential for safeguarding personal mail, documents, and packages from theft and tampering, providing peace of mind for homeowners and businesses alike. They are typically used as replacements for lost keys, broken mechanisms, or to upgrade security on existing mailboxes and, in some cases, file cabinets. Products were evaluated based on keyway compatibility, included components, ease of installation, material durability, user reviews, and feature analysis.
Prime-Line S 4140 Mailbox Lock Replacement, Multipurpose Lock for Several Brands ILCO 1003M Keyway, Opens Counter-Clockwise with 90 Rotation, Nickel Finish (1 Set)
$9.75
This Prime-Line lock offers broad compatibility and a comprehensive kit with five cams, making it highly versatile for various mailbox types.
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Mailbox Lock Replacement - Universal Mailbox Locks with 4 Keys - Easy to Install Mail Box Lock and Key Set - Durable and Secure Lock Replacement with 4 Keys for Almost All Locking Mail Boxes
$9.99
The VIXAVI lock stands out for its universal design and emphasis on quick, fuss-free installation, appealing to users seeking a straightforward, cost-effective solution.
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Prime-Line S 4573 Mailbox Lock – Replacement, Multipurpose Mailbox Lock for Several Brands – NA-14 Keyway, Opens Counter-Clockwise with 90º Rotation, Nickel Finish (1 Set)
$7.47
The Prime-Line S 4573 is constructed from robust materials like diecast, brass, and steel, indicating superior durability and long-term reliability for demanding use.
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- ✅ Universal Mailbox Lock: Now you don't have to replace your entire mailbox to add an extra layer of security. Our mailbox replacement lock is carefully engineered to fit any mailbox size or type, and comes with 4 keys and five different sizes of locks.
- ✅ Quick & Fuss-Free Installation: No handyman skills? No problem! You can quickly install your new mailbox lock set yourself in minutes without complex tools or professional help. Upgrade your mailbox's security and enjoy that much-needed peace of mind.
- ✅ The Last Mailbox Lock You Will Ever Need: Built with reliability and long-term durability in mind, our rust-resistant mailbox key lock will handle daily wear and tear without skipping a beat, ensuring your mailbox remains functional for years to come.
- ✅ Protecting Your Mail Has Never Been Easier: Prevent theft or unauthorized access to your mail with our secure mailbox lock, which is both skid- and destruction-resistant. Keep your private documents and deliveries safe with an ultra-secure mail box...
- ✅ Sleek & Modern Design: Boasting a modern aesthetic that combines style and functionality, this mailbox lock replacement kit will take your mailbox's overall appearance to the next level. Add a touch of elegance to your mailbox today with our stylish...
- Includes spring clip, mounting nut and (3) keys
- Does not include cam/latch
- C9100 operates clockwise
- Easy Replacement Lock: Quickly replaces lost or damaged mailbox locks; includes Hudson 1003M key and 5 cams for flexible fit
- Wide Compatibility: Works with many residential, cluster, and community mailboxes across multiple brands including American Device, Auth-Florence, Bommer, and Miami-Carey
- Complete Lock Kit: Includes 5 zinc-plated steel cams, brass pins, spring steel clip, and 2 keys for full installation
- Security Features: Prevents key removal when unlocked to help ensure the mailbox is locked after each use
- Installation Notes: Unlocks with a counter-clockwise turn; includes a retaining hex nut and clip for secure mounting
- [Universal Mailbox Lock] Upgrade security in seconds! This universal mailbox lock is precision-engineered to fit any standard mailbox size and type. Comes with 2 keys and 5 adjustable inserts for a perfect, hassle-free fit.
- [Quick Installation – No Tools or Experience Required] Get your lock installed in minutes, not hours. Designed for DIY simplicity, our set includes everything you need. No professional help necessary—just secure your mailbox and enjoy peace of mind...
- [TWO-LOCK BUNDLE – Double Protection for Your Home] Get enhanced security and value with two complete lock sets in one purchase. Secure multiple mailboxes—or keep a spare for future use. Perfect for households with separate mailboxes or for gifting to...
- [Built to Last – Weather, Rust & Tamper Resistant] Constructed with durable, corrosion-resistant materials, this lock withstands daily use and harsh weather. Enjoy reliable performance year after year—it’s the last mailbox lock you’ll ever need.
- [Sleek Design & Maximum Security Combined] Add a modern, elegant touch to your mailbox while ensuring skid- and destruction-resistant protection. Keep mail and packages safe from theft with style that complements your home exterior.
- S 4140 Mailbox Lock Replacement, Multipurpose Mailbox Lock with keys for Several Brands – ILCO 1003M Keyway, Opens Counter-Clockwise with 90º Rotation, Nickel Finish (10 Set)
- Replacement Lock: Suitable for replacing lost or broken mailbox locks; includes 5 cams for versatile fit options
- Fits Multiple Mailboxes: Compatible with many residential, cluster, and community mailbox styles
- Durable Construction: Made of diecast, brass, and steel with zinc-plated and nickel finishes for corrosion resistance
- Enhanced Security Design: 5-pin tumbler helps protect mail; key cannot be removed unless lock is secured
- Complete Installation Kit: Includes lock, 2 keys, cams, clip, and hex nut; installs with basic tool
- Counter-Clockwise Operation: Features NA-14 keyway with 90-degree rotation that opens counter-clockwise for secure mailbox access
- Professional Finish: Nickel-plated cylinder face provides a clean, professional appearance while offering additional protection against outdoor elements
- Premium Replacement Lock: The mailbox lock replacement parts are made of high quality zinc alloy, the cylinder surface is rolled nickel, and the locking piece fittings are corrosion-resistant galvanized for enhanced rust resistance, ensuring long-term...
- Enhanced Security: Upgrading your mailbox lock with the L-1172C mailbox lock replacement lock ensures secure access to your mailbox, providing extra peace of mind for your mail or belongings
- Easy Installation: Installation of the Mailbox locks with keys replacement is a breeze, simply remove the old lock and replace it with the L-1172C National Mailbox Lock Replacement C9100. It comes with all the necessary hardware and detailed instructions...
- Wide Compatibility: The replacement Mailbox lock is compatible with L-1172C mailboxes, which makes it easy to replace lost or damaged mailbox locks, making it the best choice for mailbox replacement locks
- ✔You will Get: 3 Pack mailbox lock replacement locks(Each packincludes 1 lock cylinder, 3 keyed alike, 65 different locking tabs); if purchasing multiple sets of replacement locks, each set of locks matched with different keys between them
- Service with Heart: Aims to provide you with high quality mailbox replacement locks to protect your safety. If you have any questions about our products, please feel free to contact us, we will reply you as soon as possible within 24 hours to solve the...
- Perfect replacement L-1172C mailbox lock, precisely compatible for USPS National Mailbox C9100, fits seamlessly without drilling or modification.
- Each lock comes with 3 original matched keys, enough for daily use and spare backup, convenient for family and multi-person access.
- Come with 10 packs per set, ideal for apartments, residential communities, property management and mailbox repair bulk replacement.
- Made of high-strength anti-rust metal material, wear-resistant, anti-pry and weather-resistant, long service life for outdoor mailbox use.
- Easy to install and replace, no professional tools required, quick installation to restore normal mailbox opening and locking function.
- Premium material: the cam locks keyed alike is made of excellent metal material made of zinc alloy, which is wear-resistant, corrosion and rust resistant, sturdy and durable for long time use.
- Easy to install: easy to install. Simply drill a hole in suitable place, insert lock head, fix tongue with fixing screw. Can be installed on metal, wood, doors, drawer panels, etc.
- Safe and reliable: the toolbox locks with keys provides you with sufficient security. Help protect privacy, assets and important materials and provide you with a safe personal space.
- Wide applications: suitable for sliding doors, cabinets, drawers, tool boxes, filing cabinets, mailboxes, furniture, RV compartments, vehicles and more. Drawer locks with keys are an extra security for important small items like documents.
- Versatile design: with 16mm cylinder length and strike plate, it can be adjusted to material thicknesses up to 12mm. This is a standard size lever lock with a diameter of 18 mm. Each mailbox lock is equipped with two identical keys to prevent one of them...
- New style C9100 USPS postal mailbox lock manufactured by Compx/National.
This article is part of our complete guide Safety & Security — browse all our comparisons and buying guides.
Last update on 2026-07-17 / Affiliate links / Images from Amazon Product Advertising API
How to Choose the Best Mailbox Locks
Understanding Keyway Types and Rotation
When selecting a mailbox lock, the keyway type and rotation direction are critical compatibility factors often overlooked. Different lock manufacturers utilize distinct keyway profiles; for instance, Prime-Line offers models with both ILCO 1003M and NA-14 keyways. In practice, selecting a lock with the correct keyway ensures that existing spare keys, if any, might be compatible or that the lock itself can be rekeyed by a locksmith more easily. Furthermore, locks operate with either a clockwise or counter-clockwise rotation to unlock. The Compx National C9100, for example, operates clockwise, while many Prime-Line models, like the S 4140 and S 4573, are designed for counter-clockwise rotation with a 90º turn. Mismatching this can lead to frustration during installation and operation.
Assessing Included Components and Completeness
The contents of a replacement mailbox lock kit can vary significantly, directly impacting the ease and completeness of your repair. A comprehensive kit, such as the Prime-Line S 4140, typically includes multiple zinc-plated steel cams, brass pins, and a spring steel locking clip, offering flexibility to fit various mailbox designs. In contrast, some options, like the Compx National C9100, explicitly state that the cam/latch is not included, meaning you might need to reuse your old cam or purchase one separately. The VIXAVI universal lock, while stressing ease of installation, bundles its lock with four keys, providing ample spares. Evaluating what's included upfront prevents additional purchases or compatibility issues down the line.
Material Construction and Long-Term Durability
The longevity and security of a mailbox lock are heavily influenced by its material construction. Locks built from robust materials are better equipped to withstand environmental elements and resist tampering. The Prime-Line S 4573, for instance, is constructed from a combination of diecast, brass, and steel, which typically translates to a highly durable and corrosion-resistant product. Similarly, the VIXAVI universal lock emphasizes its rust-resistant properties and long-term durability. In practical terms, opting for locks with solid brass pins or zinc-plated steel components, as seen in various Prime-Line offerings, tends to offer a more reliable and secure solution compared to locks made from lesser quality alloys, which might degrade faster or be easier to compromise.
Pros & Cons
Prime-Line S 4140 Mailbox Lock Replacement, Multipurpose Lock for Several Brands ILCO 1003M Keyway, Opens Counter-Clockwise with 90 Rotation, Nickel Finish (1 Set)
Pros
- Includes 5 zinc-plated steel cams for broad compatibility with various mailbox designs.
- Features a common ILCO 1003M keyway, potentially simplifying key duplication.
- Multipurpose design works with several popular mailbox brands.
- Opens counter-clockwise with a standard 90º rotation.
Cons
- Specific keyway and rotation might not be universal for all older mailbox models.
- Installation might require some understanding of cam selection.
Mailbox Lock Replacement - Universal Mailbox Locks with 4 Keys - Easy to Install Mail Box Lock and Key Set - Durable and Secure Lock Replacement with 4 Keys for Almost All Locking Mail Boxes
Pros
- Marketed as a universal lock, designed for broad compatibility across many mailboxes.
- Promises quick and fuss-free installation without requiring special skills.
- Constructed with rust-resistant materials for enhanced durability.
- Comes with 4 keys, offering multiple spares.
Cons
- The 'universal' claim might not cover every niche mailbox design.
- Specific material breakdown beyond 'rust-resistant' is not detailed.
Prime-Line S 4573 Mailbox Lock – Replacement, Multipurpose Mailbox Lock for Several Brands – NA-14 Keyway, Opens Counter-Clockwise with 90º Rotation, Nickel Finish (1 Set)
Pros
- Built with durable materials including diecast, brass, and steel for enhanced longevity.
- Works with most brands of mailboxes, offering good versatility.
- Features a specific NA-14 keyway, which is common in certain mailbox types.
- Opens counter-clockwise with a 90º rotation, a common operational standard.
Cons
- The NA-14 keyway is less common than ILCO 1003M, potentially limiting keying options.
- Only one set of keys is typically included, unlike some kits with more spares.
Common Mistakes to Avoid
Ignoring Keyway Type and Compatibility
A frequent error users make is failing to match the existing keyway type of their old lock or considering the common keyways in their area. For instance, Prime-Line offers locks with both ILCO 1003M and NA-14 keyways. Attempting to install a lock with a different keyway can lead to incompatibility with existing keys or make future rekeying more difficult and costly. Always verify the keyway type before purchase to ensure proper function and potential integration with other locks.
Overlooking Lock Rotation Direction
The operational direction of a mailbox lock is a crucial detail that often gets overlooked. Some locks, like the Compx National C9100, operate clockwise, while many Prime-Line models (e.g., S 4140, S 4573, U 9940) require a counter-clockwise 90º rotation to unlock. Installing a lock with the incorrect rotation for your mailbox's mechanism can result in the lock not functioning correctly or even damaging the internal latching components during use.
Assuming All Kits Include Cams
It's a common misconception that all replacement mailbox lock kits are complete with every necessary component. However, some products, such as the Compx National C9100, explicitly state that they do not include the cam/latch. This means users might need to reuse their old cam, which could be worn or damaged, or purchase a compatible cam separately. Always check the 'includes' section to confirm that crucial components like cams, clips, and mounting nuts are part of the package, as seen in the comprehensive Prime-Line S 4140 kit.