Both incidents had to do with bringing the boat aboard the trailer with the board partially down (inadvertently of course). In the first case I had my son raise the daggerboard, and since he did it vigorously enough that it banged loudly against the "up stop", I was confident it was all the way up. It was only after we had considerable trouble getting the boat on the trailer that I discovered that it had dropped about 6 inches. The net result was that we took one of the bunks off the trailer. Luckily the board did not suffer any damage. I vowed that I would always personally inspect the db to ensure it was all the way up before trying to get the boat on the trailer.
Last month we had a second incident. This time I inspected the board and it was fully retracted. We got the boat on the trailer OK, but as we were pulling over the crest of the boat ramp I heard a dragging sound...the board had managed to come loose and dropped enough to contact the ground. It could not be pulled up, however, because it was wedged between a trailer crossbar on the leading edge, and the back of the db trunk on the trailing edge...we had to back the boat into the water again to get it free.
My "permanent solution" is to add a "U"-shaped bracket to the top of the db through which I can slide a short rod that will lie completely across the upper db deck opening, thus making it impossible for the db to drop, regardless of what happens to the db halyard.

