I managed to buy an excellent rear screen for my car ,from a member and I`m starting to fit it .I have all the rivets in place but a problem with the slider .Even with only the actual screen in the slider I am unable to get it to move along the zip .Is there a recommended lubricant I would have thought it would slide up and down the zip  easily without both part being fitted Also there is no metal tab on the one zip side I can  possibly get over this when I get the slider to move  Len