I am looking at a couple of devices that assist those of us that hook up their trailers by ourselves. One are two simple rods with magnets on the bottom that are placed on the hitch ball and coupler. They are then lined up when backing. A second is a metal V shaped plate that goes behind the hitch ball, the idea being that it will,upon contact, guide the coupler over the ball. Has anyone used these or other devices and found any particular one that works as advertised?