I have locks and security cables on everything. None of it will stop a determined thief, but it will slow them down and cause them to make noise ... It will sure as hell prevent petty larceny by casual thieves, specially if one is having lunch, or a twinkle!
e.g. A security D riveted to the water Jerry can. It also prevents it from being opened when locked onto the trailer:
When I start to add up what's hanging off the outside of our trailer, it's worth quite a bit:
2x 20L steel Jerry cans, one full of fuel, the other water;
2x gas bottles
Spare wheel and tyre, plus the wheels and tyres on the trailer axle ...
Jockey wheel ...
Leaving aside what's in the tool box and trailer tub!
All adds up to a very tidy sum.
A friend 'lost' the spare wheel off the roof basket of his car while filling up at a servo in the NT.