Your biggest truck camper mistake?

My most spectacular mistake so far was laying the propane igniter gun used to light the oven on the stovetop grill ... with one of the burners going. Kaboom! Gave me a good scare but luckily didn't do any serious damage. Of course you already know how to handle nearly every aspect of traveling with a truck camper after your years with a travel trailer. One thing I can thing of that is different is that truck camper rigs are taller than travel trailer rigs so you have to know your height and watch for anything you won't fit under.