This is my post for 
A few years ago, I was leaving to go fishing. I made it partway down our driveway, and my boat trailer jumped off the truck. I had put my boat trailer on the hitch of the truck but forgot to hook it! and put the lock on it. I could not lift it to the truck or high enough to put the little wheel down. I had to walk back to the house and get a low jack, the jack in my truck would not fit under it. The jack would not get it high enough either, so I had to walk back to the house and carry bricks back to the truck, where I could jack it in stages. All of this before going fishing made for a short day of fishing.
I was lucky it happened there instead of on the highway. I have seen boat trailers jump off trucks on the highway, some flipped and some ran off the road and up a berm with plants in front of a housing development. The plants stopped the boat and trailer from going into a house, there were all sorts of things scattered down the road, coolers, life jackets, and fishing poles, etc.
When I went with my sister a few days ago to buy a trailer for her lawn mower, I took a lock with us so we would not have the trailer jump off while going down I95, but when we got there, the trailer hitch was not like the kind we have on our boat trailers. I could not put a lock on it. I told the guy I did not like the idea of us taking it that far with no way to lock it down. It was something I had never seen, the latch slid instead of lifting up. We found a piece of wire and wired it so it could not slide. We made it back with no problems.
photos are mine