Got a C-118A cargo plane? Trying to figure out where you can put the troops so that load of tangerines doesn't unbalance the plane? Well, here's the tool for you, champ. The rule seems to be made of something between plywood and plastic, and is fairly heavy. Apparently, the military had these for various types of planes, so if you don't have a C-118A and you still want to know where to load the bombs, you can probably find the appropriate rule. See also the V-69 V-69 Hey! for what happens when the people who use these things start indulging.