When pulling my boat, I always get nervous when someone pulls up behind me at stop signs and traffic lights. They ALWAYS look too close. I added a flag to the engine as a focal point for that driver, rather than have them pick my truck, trailer or boat as a stopping point. A strap could cause rub marks on the engine paint and there weren't many spots to clip a flag to.
The idea came to me to use the water flushing hose connection. Using a plastic male hose repair connector, I drilled a pair of holes and threaded a ty-wrap through the flag and connector. It screws snugly to the engine, but I laced a string to it until I'm sure the connector won't back out.
Hopefully the pics will come through.