Whenever my camper is parked at the security lot or at home, I keep a lock on the king pin. I know locks are the kind of things that keep honest people honest, but it gives me a bit of peace of mind. I don’t lock the king pin when we’re camped as I figure the fully setup camp and 4 slides will dissuade any would-be evil-doers from making off with my apartment on wheels.
I use a simple Husky fifth wheel lock. It is easy on/easy off.
The only issue is that I do grease the king pin and the lock picks up some of that. I generally handle the lock by the portion where the key goes in and hold onto it from there. But, I’ve ended up with grease on my hands more times than not. (sad face)