they've only got to watch you to see which part of the workshop you use most to see where your tools are.
I have heard of people trying to misguide thieves and most little pikeys are fooled but the pro's watch your place for days before the robbery, they check when you come and go, what your habits are etc.
I used to work in a shop that sold tools so i spoke to lads with vans, some who had workshops etc. If you leave your tools in a van it's a nightmare, I heard of one van left on a site while the owner went for a drink, when he got back thieves had cut the side door out
Units, normally thieves use bog windows, and I have heard of some coming through roofs. Gates no matter how beefy, can often be broken at where lock plates meet.