You can buy hard bike covers (a bit like a mini-garage, I suppose) and you can install anchors, sunk into concrete or fixed into a wall, but they're not always an option. There's always somewhere where your bike is vulnerable. I had two nicked in the space of a year, prompting a visit from the claims investigator "So, Mr *Bob*.. (fixes me with icy stare).. you seem to be losing an awful lot of motorcycles, mmmm?" Buying heavier or less desirable (or both) machines seems to be the best deterrent. Sad, but true.