Did not think this was a big deal until I saw my 60 year old father crawling under our boat to retreive a rope he had "thrown" under the boat to secure the cover to the boat. Some of you probably have better ways of tossing a boat cover rope under the boat but this is the best way I've found that doesn't include using other items.

All I do is take the end of the rope, wrap it around my hand three times (to create a "ball" of sorts), make sure the rest of the rope (probably 6-8 feet or so) is laying on the ground (or hanging) between the boat and the trailer (as opposed to outside the edge of the trailer) and I toss the wrapped end of the rope to the other side.

I can usually (95% of the time) get the rope all of the way over past the edge of the other side of the trailer so I don't have to crawl under the boat at all. Hope this helps someone who may be struggling with the same problem my dad was having.