FOr my shed I put in extra long screws that screwed into 2×4 behind each joint. and corner. I then rounded the heads of each screw with a drill.
I repeated the same process for any other area that has screws in it.
The door has 2×4 all across the back where any screws go in.
Inside the door I have a vertical and lower bolt.
Vertical bolt goes up into a piece of 2×4 bolted into the frame with long screws and is locked.
large Floor bolt goes through the floor into the concrete slabs.
Difficult to open second door now to get bikes out.
I lifted one of the concrete slabs and bolted an expensive U lock through it after drilling holes for my ground anchor. It comes up through the floor and into the shed.
Bikes are secured with two chains. joined by circular ‘uncroppable’ reenforced locks. chain loops up to the top of the hut where again another bit of 2×4 has been bolted in place with a metal hoop secured there as well
Outer lock is another circular anti-crop lock reenforced.
The security was put in place by a mate who in the past has possibly entered a few sheds without permission.