Between your wing nuts and the slider bars that keep your Safari windows open should be phenolic washers. This is how Safari windows have been designed by Volkswagen originally. 

These special washers protect the chrome (or paint) from your glider bars and make sure you can clamp the window in every desired position. Many aftermar

ket brands use plastic or nylon washers which has a different effect. You need one on each side of the glider bar per wing nut, so a total of 8 pcs per car. Sold each.