Key safe for a Swiss post box / Milchkasten compartment
A simple, discreet way to share your keys – installed without drilling, completely battery-free, with a choice of removable Velcro or permanent adhesive fixing.
A key safe inside a Swiss post box or Milchkasten keeps a key available at the property without the need to drill into the outside of the building and, with the Velcro option, without making a permanent fixing. It is useful for families, Spitex / home care, cleaners, holiday rentals, tradespeople and many other situations. The safe is discreet, protected from direct weather and available whenever an authorised person needs access.
The 6 things to check before buying
For most customers the decision comes down to six questions. Check these first.
Is it suitable for a standard Swiss post box?
Yes. These models are designed for standard Swiss post boxes with a Milchkasten or lower compartment. We sell them specifically for this use and have not encountered a compatibility problem with a standard Swiss box.
Velcro or adhesive?
Both are no-drill installations. Choose Velcro if you want the safe to be removable later; choose adhesive when you want it permanently fixed in place.
Wheels or push buttons?
Number wheels are familiar and compact. Push buttons are quick and can be easier for elderly users, people with reduced finger dexterity, and when using the safe in cold weather.
Will the post box still work normally?
Yes, provided the safe does not obstruct the letter slot, door, hinges or the route taken by the post.
Can I change the code?
Yes. The mechanical models shown here have changeable codes. Always record the new code somewhere secure.
Does it need batteries?
No. All the models on this page are fully mechanical – no batteries, app or internet connection.
Of the models shown here, it is our first choice when security, robustness and reliability are the priorities. It installs without drilling and can be removed later.
Why install a key safe inside the post box?
For many Swiss homes the biggest advantage is simple installation without drilling the building. This is particularly useful in rented apartments, where drilling into the building may not be permitted or desirable. The safe sits neatly inside the existing Milchkasten, remains discreet, is protected from direct weather and gives authorised users quick, easy access to the key.
Discreet
There is no obvious external key safe visible from the street.
No drilling
Both Velcro and adhesive versions can be installed without drilling the building or post box.
Access when needed
Authorised users can obtain the key even when nobody is home, while the owner keeps control by changing the access code whenever required.
Fully mechanical
No battery, app, updates or account to manage.
Will a key safe fit my Swiss post box?
Yes. The models shown here are designed for standard Swiss letterboxes with a Milchkasten or lower compartment. We sell them specifically for this use and have not encountered a compatibility problem with a standard Swiss box. You do not normally need to measure before ordering. Product dimensions are also shown with each model.
- Position the safe so that the door, hinges and mail path remain clear.
- Check that the compartment door can still open fully.
- Leave enough room in front of the buttons or number wheels.
- Do not obstruct letters or smaller parcels.
- Where space is tight, the Master Lock 5401 is generally the most compact option in this range.
The rear wall often provides the largest flat surface and easy access to the code. A side wall may be better if it improves opening clearance or leaves more room for post. The best position is discreet, comfortable to use and clear of all moving parts.
Velcro or adhesive – which fixing is better?
Both systems install the key safe without drilling. The real difference is simple: Velcro is removable; adhesive should be regarded as a permanent fixing.
Choose Velcro when you want the safe to remain removable
Velcro is our most flexible post-box solution. The safe can be removed later without leaving a permanent fixing, making it particularly suitable for rented apartments, temporary requirements or any situation where the access arrangement may change. If it is fitted again in another position, new Velcro will be required.
- Safe can be removed later without leaving a permanent fixing.
- Particularly useful in rented apartments.
- A good choice when the requirement may be temporary or may change.
- Strong fixing when applied to a clean, dry and suitable internal surface.
- Use the purpose-prepared Velcro version supplied for this installation; new Velcro is required if the safe is later installed in a different position.
Choose adhesive for a permanent installation
Adhesive should be considered a permanent fixing. It is ideal when the key safe is intended to stay in the same position long term. As with any bonded installation, the internal surface must be properly prepared and the adhesive allowed to cure fully.
- Permanent fixing.
- Ideal when the safe is intended to remain in one position long term.
- Clean and degrease the surface carefully.
- Do not load the safe until the adhesive has fully cured.
- The adhesive fixing should be treated as permanent and is not intended to be removed.
How secure is a key safe inside a post box?
A key safe inside the Milchkasten is a particularly discreet and secure way to provide controlled access to a key. The safe is hidden from normal view and protected inside the post box rather than displayed on the outside of the building. Attacks on key safes are uncommon, particularly when the safe is not visible. Choose a good-quality model, keep the code private and change it whenever access requirements change.
- Only give the code to people who genuinely need it.
- Change the code when a service provider no longer needs access.
- Avoid obvious codes such as birth years or 1234.
- Position the safe so the code cannot easily be observed from outside.
- For frequent or professional use, choose a more robust model.
What is the police position?
Police security advice generally favours keeping keys secure and out of sight rather than hiding a loose spare key around the property. A mechanical key safe provides controlled access through a code, and placing it inside the Milchkasten has the additional advantage that the safe itself is not normally visible. As always, use a good-quality safe and keep the code confidential.
What about insurance?
Using a key safe does not mean leaving the property unlocked or leaving a key freely accessible: the key remains protected behind a coded mechanical lock. Forced entry into a locked key safe is an attack on a security device. Individual policy wording can of course vary, so if you have a specific insurance concern you can check it with your insurer.
Who is a post-box key safe useful for?
The principle is simple: a key remains available at the property for authorised users. That makes this useful far beyond home-care applications.
Which code system is easier in winter?
Both systems are battery-free. The Master Lock number wheels are familiar but require small dials to be turned. Push-button models such as the KeyGuard and Supra S5 avoid that movement and can be easier for some users with cold fingers or thin gloves. The best choice depends on the user's dexterity.
Why do some models have a weather cover?
A cover protects the keypad or wheels from dirt and makes the code mechanism less visible. Inside an already protected compartment it mainly adds another layer of protection and discretion.
Which key safe should I choose?
This is the simplest way to choose between our main post-box models.
Master Lock 5401 + Velcro
A compact, good-value key safe with the familiar four-wheel combination system. Simple to use and well suited to families, rentals and everyday access.
More info →Burton KeyGuard + Velcro
An excellent choice where several authorised people need regular access, for example Spitex, cleaning companies or property services. The mechanical push-button keypad is quick and easy to use, particularly for frequent users, elderly people and anyone who finds small number wheels difficult to manipulate.
More info →Supra S5 + Velcro
Our strongest all-round recommendation for a Swiss post box. The Supra S5 is exceptionally robust and reliable, with a proven mechanical design built for years of regular use. Combined with Velcro fixing, it provides a high-quality no-drill installation that can be removed later if required. An excellent choice for both private and professional use.
More info →Supra S5 + adhesive
The same exceptionally robust and reliable Supra S5, installed with high-strength adhesive for a permanent fixing. An excellent choice where maximum durability and a long-term installation are the priorities and there is no requirement to remove the safe later.
More info →Quick comparison
Price is only one factor. Also consider the available space, code style, frequency of use and whether the safe may need to be removed later.
| Model | Best for | Code | Fixing | Main strength |
|---|---|---|---|---|
| Master Lock 5401 | Everyday / value | 4 wheels | Velcro | Compact and popular |
| Burton KeyGuard | Regular / professional | Push buttons | Velcro | Fast and easy to share |
| Supra S5 Velcro | Frequent / robust | Push buttons | Velcro | Robust and removable |
| Supra S5 adhesive | Long-term installation | Push buttons | Adhesive | Robust and permanent |
Common mistakes to avoid
- Positioning the safe where it obstructs post, the door or hinges.
- Applying Velcro or adhesive to a dusty or greasy surface.
- Choosing a position where somebody outside can easily watch the code being entered.
- Using an obvious code or failing to change it when a service provider no longer needs access.
- Failing to record a changed code somewhere secure.
- Putting load on an adhesive installation before it has fully cured.
Post-box key safe models
Master Lock 5401 key safe with Velcro for Swiss post box
The Master Lock 5401 with Velcro is a simple and economical way to install a mechanical key safe inside a post box, parcel compartment or other protected location without drilling.
Its resettable 4-digit combination is straightforward to use and requires no batteries, electronics, smartphone or app. The internal compartment holds up to 5 keys depending on their size.
Heavy Duty Velcro means the safe can also be removed later if required. We recommend it when price, simplicity and removable installation are the main priorities.
- Heavy Duty Velcro 10 × 5 cm, up to 7 kg according to manufacturer
- Suitable down to –30 °C according to manufacturer
- Drill-free, removable installation
- Resettable mechanical 4-digit combination
- Holds up to 5 keys depending on size
- External: 120 × 83 × 38 mm
- Internal: 90 × 64 × 27 mm
More info
The Master Lock 5401 with Velcro is a simple and economical way to install a mechanical key safe inside a post box, parcel compartment or other protected location without drilling.
Its resettable 4-digit combination is straightforward to use and requires no batteries, electronics, smartphone or app. The internal compartment holds up to 5 keys depending on their size.
Heavy Duty Velcro means the safe can also be removed later if required. We recommend it when price, simplicity and removable installation are the main priorities.
- Heavy Duty Velcro 10 × 5 cm, up to 7 kg according to manufacturer
- Suitable down to –30 °C according to manufacturer
- Drill-free, removable installation
- Resettable mechanical 4-digit combination
- Holds up to 5 keys depending on size
- External: 120 × 83 × 38 mm
- Internal: 90 × 64 × 27 mm
Burton KeyGuard key safe with Velcro for Swiss post box
The Burton KeyGuard with Velcro is our budget push-button option for shared access where you want a drill-free, removable installation. The Velcro fixing can be fitted to a suitable, properly prepared surface and removed later if requirements change.
Its 12-button mechanical keypad needs no batteries or electronics. It also has a useful advantage over wheel combinations: the code you enter is not left visible after use.
Despite its accessible price, the KeyGuard has a robust metal body, a protective rubber cover and genuine capacity for 3–5 standard Yale keys. It is a practical choice for family access, rentals, holiday homes or service access, and a lower-cost alternative to the Supra S5 Velcro.
Specifications:
- Velcro fixing for drill-free, removable installation
- 12-button mechanical keypad with no batteries
- No code left visible after use
- Robust metal body with protective rubber cover
- Capacity: 3–5 standard Yale keys
- Keys up to 80 mm
- External dimensions: 115 × 65 × 55 mm
- Internal dimensions: 80 × 40 × 20 mm
- Weight: 0.7 kg
More info
The Burton KeyGuard with Velcro is our budget push-button option for shared access where you want a drill-free, removable installation. The Velcro fixing can be fitted to a suitable, properly prepared surface and removed later if requirements change.
Its 12-button mechanical keypad needs no batteries or electronics. It also has a useful advantage over wheel combinations: the code you enter is not left visible after use.
Despite its accessible price, the KeyGuard has a robust metal body, a protective rubber cover and genuine capacity for 3–5 standard Yale keys. It is a practical choice for family access, rentals, holiday homes or service access, and a lower-cost alternative to the Supra S5 Velcro.
Specifications:
- Velcro fixing for drill-free, removable installation
- 12-button mechanical keypad with no batteries
- No code left visible after use
- Robust metal body with protective rubber cover
- Capacity: 3–5 standard Yale keys
- Keys up to 80 mm
- External dimensions: 115 × 65 × 55 mm
- Internal dimensions: 80 × 40 × 20 mm
- Weight: 0.7 kg
Supra S5 key safe with Velcro for Swiss post box
This version combines the Supra S5, one of our most robust and proven reliable mechanical key safes, with a heavy-duty Velcro fixing. It can be installed discreetly inside a post box, parcel compartment or other protected location without drilling.
The 10-button mechanical system needs no batteries, electronics or app. It is simple to operate, proven over many years of use, and the code can be changed whenever authorised users change.
The Velcro fixing makes the installation removable and reversible. The safe can be taken away later if it is no longer required, making this particularly useful where a permanent fixing is undesirable.
- Supra S5: exceptionally robust with proven long-term reliability
- Heavy-duty Velcro fixing approximately 9.5 cm
- Drill-free, removable and reversible installation
- 10-button mechanical code with no batteries or electronics
- Code can be changed whenever authorised users change
- External: 108 × 58 × 51 mm
- Internal: 70 × 38 × 32 mm
- Weight: 0.9 kg
More info
This version combines the Supra S5, one of our most robust and proven reliable mechanical key safes, with a heavy-duty Velcro fixing. It can be installed discreetly inside a post box, parcel compartment or other protected location without drilling.
The 10-button mechanical system needs no batteries, electronics or app. It is simple to operate, proven over many years of use, and the code can be changed whenever authorised users change.
The Velcro fixing makes the installation removable and reversible. The safe can be taken away later if it is no longer required, making this particularly useful where a permanent fixing is undesirable.
- Supra S5: exceptionally robust with proven long-term reliability
- Heavy-duty Velcro fixing approximately 9.5 cm
- Drill-free, removable and reversible installation
- 10-button mechanical code with no batteries or electronics
- Code can be changed whenever authorised users change
- External: 108 × 58 × 51 mm
- Internal: 70 × 38 × 32 mm
- Weight: 0.9 kg
Supra S5 key safe with adhesive for Swiss post box
The Supra S5 is one of our most robust and proven reliable mechanical key safes. This version uses Pattex adhesive to provide a drill-free installation on a smooth, dry, degreased and correctly prepared surface.
Its 10-button mechanical system requires no batteries, electronics or app, and the code can be changed whenever authorised users change.
Unlike the Velcro version, this is intended as a more permanent installation. It is particularly useful inside a post box, milk box, parcel compartment or other protected location when you want a clean fixing without screws.
- Supra S5: exceptionally robust with proven reliability
- Pattex adhesive: –30 °C to +80 °C, according to manufacturer
- Drill-free mounting on a correctly prepared surface
- More permanent fixing than the Velcro version
- Resettable mechanical 10-button code
- Protective cover included
- External: 108 × 58 × 51 mm
- Internal: 70 × 38 × 32 mm
- Weight: approx. 0.9 kg
More info
The Supra S5 is one of our most robust and proven reliable mechanical key safes. This version uses Pattex adhesive to provide a drill-free installation on a smooth, dry, degreased and correctly prepared surface.
Its 10-button mechanical system requires no batteries, electronics or app, and the code can be changed whenever authorised users change.
Unlike the Velcro version, this is intended as a more permanent installation. It is particularly useful inside a post box, milk box, parcel compartment or other protected location when you want a clean fixing without screws.
- Supra S5: exceptionally robust with proven reliability
- Pattex adhesive: –30 °C to +80 °C, according to manufacturer
- Drill-free mounting on a correctly prepared surface
- More permanent fixing than the Velcro version
- Resettable mechanical 10-button code
- Protective cover included
- External: 108 × 58 × 51 mm
- Internal: 70 × 38 × 32 mm
- Weight: approx. 0.9 kg
Frequently asked questions
Is it suitable for Swiss post boxes?
Will post still fit?
Can a Velcro model be removed later?
Why choose Velcro instead of adhesive?
Why choose adhesive instead of Velcro?
Which model is the most popular?
Which model do we recommend for professional use?
Which is the most robust?
Can children or other people see the numbers?
Rear wall or side wall?
Is it easy to use in winter?
Why do some models have a cover?
Can I change the code?
What if I forget the code?
Does it need batteries?
How much does it cost?
What if a post-box safe is not the right solution?
This site is not only about post-box key safes. If you prefer a wall-mounted safe or your security requirements are different, see our complete range of mechanical key safes.
