Garage door security is a subject that raises my blood pressure just to think about. Most garage doors are made of thin plywood or hollowcore filled with foam. When you get right down to it the doors themselves are usually pretty flimsy. The locks that are installed on them are also often not well made and seem like an afterthought. Who thought t-handles were a good idea? I would avoid anything that is easy to force over with a wrench on the exterior of my building.
The first step after making sure the garage door is shut is to get a good lock on your garage door. Manual garage doors often use a system of spring-loaded latches that snap into place when the door shuts and are released by twisting something in the middle of the door that retracts those latches which are connected by steel cable. This device can be a rim cylinder which is difficult to force because it is flush with the door and protected by a tapered ring.
There are also steps to secure motorized liftup garage doors. They are frequently installed with an override cable connected to a little wafer lock on the garage door at eye level. I disconnect this cable from my garage door because I know how easy it is to pick this lock or drill it. I also ensure that the override is zip tied down so that thieves can’t try to catch it with a hanger.
Another vulnerability with garage doors are keypads or keyswitches wired directly into the opener. Back in more honest times maybe they did their job but a keyswitch that is held in with two finishing nails doesn’t cut the mustard. When you get access to the wires and bridge them, that opens the door. All access to those wires must be protected. If I was going to attach something to these wires on the exterior of the garage it would be covered with a lot of thick steel and would require real work to remove. If you have wires connected to the back of some device on the exterior I advise you to replace that device with one that operates via radio instead. Then when someone pries the plastic thing off the wall they will still not have access.
A new solution has been provided for liftup garage doors. I’ve never installed one but it looks pretty easy. It integrates with existing electric opener or could be used with a manual liftup.
Other options include padlocks and hasps. This is kind of a nuclear option because it requires getting out of your vehicle to unlock. Sometimes it is the only way to secure a garage door, especially after one has already been forced open by prying or other means. I have installed hasps at the bottom of the door in concrete or at the side in wood. The important thing is to ensure that the screws are covered by the hasp.
Similar to the hasp option is a slide bolt and hasp. These
This thing looks like a pretty good nuclear option. Doesn’t look like it’s available in the USA. Similar in function item that would manually secure a liftup door. Abloy manufactures a garage door lock that would replace a t-handle. The Abloy RI009 would be a lot harder to force over with a wrench than a $25 t-handle but it also retails for over $700! None of the locks in this paragraph would be terribly convenient to use but are all capable of withstanding more force than the door itself probably is.
The next step is getting a commercial steel door but that is a lot more money and may be more than whatever you have inside your garage.
There are options to lock your liftup garage door.