I don't have the manual in front of me, but if I remember correctly, the 1/16" spacer is to space the rail that is mounted on the bottom of the hatch from the outside edge so the hatch seats completely yet not let the hatch slop around from side to side. Like I said, I don't have the manual in front of me, but if you don't get any responses I'll post a more knowledgable answer when I get home.