I put only one on each corner. Controls the forward back movement with the scissors jacks. Certainly helped, but may put another on each corner to control side to side movement.
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2007 Ford F250 4x4 Harley-Davidson Powerstroke
2006 Cedar Creek Silverback - 35 LRLBS
(2012 -11) (2013 - 10 so far)
I put only one on each corner. Controls the forward back movement with the scissors jacks. Certainly helped, but may put another on each corner to control side to side movement.