Never used them, no need to. Soooo.... the camper rocks a little. It reminds of the Carnival Cruise we took a few years ago.... laying in bed, every now and then, you could feel the ship movement... One night, it happened. I asked my wife, there beside me, "Hey, did you feel that?" She said, "Yes". I said, "That kind of felt like the trailer when it rocks a little, doesn't it?" She said, "Yes."
Well ... maybe the cruise ship feels like a trailer rocking!
Either way, they are not needed. Your slides are made to be supported properly. If you want to eliminate movement, keep any and all jacks under the main trailer frame. You'll be much better off that way.