Best Garage Door Defender: Level Up Your Security



Most up and over garage doors have a standard cylinder lock or frame bolts built into their handles.

These are better than nothing and can act as a deterrent.

But a skilled thief can get through them in moments – and with less noise than you’d think.

Thankfully, there are a few (relatively) simple ways to improve security and one of the first to consider is the garage door defender.

Our Top Pick

Bulldog GD20

Strong Visual Deterrent

The Bulldog GD20 is going to present problems for a thief no matter what way they come at it.

Also relatively easy to fit. Check Amazon

Tamper Proof

Asec AS1997

Cost-Effective Solution

Installing the Asec AS1997 system is a bit more involved, but breaking through it would be both difficult, noisy and require at least two cuts. Check Amazon

Best Garage Door Defender Reviews

Let’s jump into our top recommendations.

Bulldog GD20

This is a quality locking system that acts as a strong visual and material deterrent.

Check Prices on Amazon

4 bolts (not included) secure the base plate to concrete, block paving, or any hard surface, and the steel bar is locked in place.

Like the Garage Defender though, it needs a flat surface for installation.

That aside, there’s not much to complain about here.

The shackle is hard to access with power tools, and the design means there’s no obvious weak point to attack with a grinder.

It’s cheaper than some other options on the list and offers comparable security to the best of them.


  • plus iconQuality solution at its price point
  • plus iconBright red makes it a better visual deterrent


  • minus icon Needs a flat surface

Asec As1997

This solution involves mounting two sliding bolts to your garage door then drilling holes in the frame on either side to accommodate them in the locked position.

It’s a bit of work but is a genuinely good security product for the price.

Check Prices on Amazon

The two units are attached to the inside of the door and are difficult to tamper with from the outside.

Unfortunately, it doesn’t really offer any visual deterrent to opportunistic thieves. The only evidence that it’s been installed is the four bolts on either side of the door.

Career burglars might recognise these and move on.

If they did try to pursue a break-in, it would be a noisy, drawn-out affair as both bolts need to be cut and are difficult to access from outside.

We like that this can be opened from inside or outside using the four-sided keys provided.


  • plus iconCost-effective security
  • plus iconNear tamper-proof


  • minus icon Doesn’t act as a visual deterrent

Bulldog GD400

This is a high-quality garage door lock that differs from the others in its design.

Check Prices on Amazon

Unlike the other examples (with the exception of the Asec), part of the GD400 mounts to the garage door.

Directly below the angle bracket on the door, you drill a hole to house the lock tube.

Once this lock tube is cemented in place you can close the door, drop the lock bolt in place, turn the key and place the dust cap on.

Your door is locked with no quick or silent way of being opened.

This is a heavy-duty, high-security option that we really can’t find fault with.

If you’re securing a particularly beautiful, vintage bike, or money isn’t an issue – this is probably the solution for you.


  • plus iconWill work just about anywhere
  • plus iconHigh security


  • minus icon Expensive

Garage Defender Master

This powder-coated steel solution is anchored to the ground by two bolts. One sits inside the closed door and the other is covered by this unit’s ‘hockey puck’ style lock.

This lock holds down the large steel bar, meaning the door can’t be opened. It’s a good deterrent.

Check Prices on Amazon

They’ve hidden the weakest point of the lock (the shackle) inside the unit and when installed correctly the anchor bolts are also inaccessible.

The main drawback of this and every other system like it, is that it requires a flat surface to install the base plate.

Most UK garages I’m familiar with have either a step-down into the driveway, or a raised ridge along the threshold to prevent flooding.

Without either using a jackhammer to make a flat area or pouring concrete to make a raised, flat area – these systems can’t be installed.


  • plus iconTough, well-designed solution
  • plus iconWeakest points hidden
  • plus iconGood visual deterrent


  • minus icon Needs to be installed on a flat surface
  • minus icon Cheaper, comparable options available

Buyer’s Guide

Types Of Door

Our list was mostly focused on securing up and over style garage doors, but models like the Bulldog GD20 and the Garage Defender Master, work equally well outward opening double doors.

We covered up and over garage doors for a reason.

Typically, these doors are secured by turning a handle that throws two lock bolts at the edge of the door into lock tubes in the door frame.

The problem is – the cylinder your key goes into can often be drilled out and turned without too much trouble. 



Most of these locks require a bit of work to install.

Like we mentioned before, Bulldog’s GD20 and the Garage Defender Master need a flat surface to install the base plate correctly.

If your garage has a step-down, kerb, or raised area to prevent flooding – look at the other solutions.

The Bulldog GD400 mounts to the door via four blind bolts, but you will need to drill/chisel a hole in the ground big enough for the lock tube then cement it back in place.

Alec’s AS1997 solution is fairly simple if time-consuming to install.

Each bolt mechanism is secured to the door by bolts, and holes must be drilled in the door frame to accommodate the lock bolts.


Why are the benefits of a garage door defender?

Unfortunately, there’s no perfect security solution. If a professional (hate to use the word, but it fits) wants to break in – they will.

What your money buys you is time, hassle (for the bad guys) and noise.

All these solutions work by greatly increasing the inconvenience (power tools required), time and noise levels of opening a garage door.

By hiding the anchor bolts and shank then using blind bolts for fixing – these locks deny would-be thieves access to a lock’s usual weak spots.


Other Security Options

There are a number of other ways to improve the security of your bike at home.

A ground anchor is an effective deterrent and will cause real problems for thieves committed to stealing your bike. Pair this with a good quality security chain and a disc lock and you’ll have made life significantly harder for the low life’s.

See our article on motorcycle security for a more in-depth look at your other options.



Garage burglary is a genuine problem. Most of it is opportunistic, so having any kind of aftermarket locking solution will help.

If your bike and tools are in the garage, it’s worth spending a percentage of their value on a security system.

What percentage is up to you. I lock my bike (which I value at about 1500 GBP) with a 150GBP lock – as an example…