facory wrote:
Recommendations for what is thought to be a theft proof lock? Include a link to the website selling it.
No such animal exists. There are a lot of resistant locks, but even the best isn't going to stand up to a cordless angle grinder for long.
An alarm that hits the e-brakes is a good idea, especially if the battery for it is in a hard to access location. It is defeatable, but would take more time than just taking a bolt cutters to a shackle. I would also add a solar panel and charge controller so the battery that would activate the trailer brakes is topped off.
The best thing to add to a security system, if one owns the property the trailer is on, wouldn't hurt to add a couple camera traps, especially the ones that automatically upload images to a website, so if they are found and smashed, the images will still be obtainable.