New Leader has recently started using rubber sleepers that are welded onto the bottom of the frame rails of their fertilizer spreader boxes. These are a rubber pad with a metal backing that take the place of the wooden sleepers that have been traditionally used between the box frame rails and the machine frame rails.
Note: The 9" long pad is used at the rear of all the spreader boxes (2 used). The 5" long pad is used on the frame cross rails and mounting tie-down points (11' and 12' boxes require 8, 13' and 14' boxes require 10).