seen them on lowloaders on the A14 before, part resting on the front raised bit the rest of it propped up on stilts, leaves a big gap underneath it for sheet metal etc 
You can see this one is well secured with a piece of rope, and then it goes over the roof to the opposite casting, it was the way forward until the dockers put a stop to it, but even then if you had two working twistlocks they would load you 
