My shop has no windows.
1 – For security. If no one can see what is in there, they won't be quite so tempted to steal it.
2 – Also, being fairly small, the lack of windows allows more shelf space.
The door is a secondhand fire door, and came with a 6 lever lock. So it would be more difficult to cut through or to pick the lock.
Since the hinge pins are visible, externally, but not easily accessible, I fitted hinge bolts. These are merely woodscrews, about 3 mm in diameter, about 70 – 80 mm long, with the heads turned down to match the shank.. Two or three are screwed into the back edge of the door, by gripping in a drill chuck and screwing in until about 15 – 20 mm still protrudes.
By trying to close the door, the hinge bolts mark the door post, showing where to drill. The hole does not need to be a very tight fit, just enough clearance for the modified screw to enter.
If the lock is not unlocked, the door cannot be lifted out after driving out the hinge pins.
Cutting through the walls or roof, will be difficult, but not impossible, since there is cladding, at least 12 mm thick on each side of 50 mm frames, with glass fibre insulation between the frames, and cladding.. Not impossible, but slow and a bit messy, for the burglar.
It is unlikely that any thief would be slim enough to crawl between the 200 x 50 mm bearers, on 300 mm centres to cut through the floor. And there is very little area not covered by something heavy!
Hopefully any potential thief will think it not worth the effort and seek easier pickings.
The garden is surrounded by 1.7 metre high fences, with plenty of bushes against the fencing., so again, not such an easy task to cut through, especially with neighbours on each side, who might spot what was happening.
HTH
Howard