its a wonder my tools/van hasnt been nicked 10 times over, the amount of times i forget to lock it!
most vans back doors will close on a microbore pipe without crushing it, and then you can lock it too. thats what i do.
it is very tempting to leave the back doors open after walking all the way around the back, but after the scare storys on here, its just not worth it!
we all should put those steering wheel disc locks on everytime we leave our vehicle, i do at night but not in the day, maybe i should?