"Ivan, we have an overstock of canal barges, railroad engines and wooden bridge supports. What shall we do with them?
"Simple Gregor. Stick the engines onto the bridge supports, and then fasten the supports to the canal barges. Add some machine guns and bombs, and we're in business !".
Those guys had big ones - sliding off the wing, climbing out of various hatches to 'jump', and no static lines, just a short free-fall and pull the ring !