Im looking for some clues on how this particular thread guide plays a role. Adjustment of this guide is up or down and can be turned and mounted upside down.  This is on Juki 1341, 1541 several 1500 series and I have seen it on some other brands including Consew https://www.sewingpartsonline.com/thread-guide-juki-21355805.aspx in the below pic, item 9 is the location       Thanks for your help, its appreciated Floyd