I got a Singer 4-thread serger a few months ago. Had one basic class, then the rest of the classes were postponed. I want to do a 1/8" rolled hem for scarves. My manual says to use "the spreader". What is the purpose of the spreader. I tried putting it in, but was unsure if that looper should be threaded or not. It was and the thread kept breaking. Any advise out there?