When I lived in Panama City I bought a smal 16' aluminum boat with 20 hp motor from a guy. The first time I took it out I backed down the boat ramp to the edge of the water..got out and undid the strap. The slope was not that steep so I went ahead and unhooked the boat from the trailer. What I did not know is that the previous owner for some reason or another had attached teflon strips the length of the running boards on the trailer. The boat shot off the trailer, prop caught on the ramp and the boat stood straight up like it was about to tip over. I was just thankful no one else was there to see this. The boat and all was fine. I still do not know why someone would do this, but I will be more careful from no one when backing in a boat I have not used before.