On all of my tables I have installed a flat head screw with a rubber washer about six inches out and to the right of the needle path. Then, before engaging power I grab both threads (upper and lower) I wrap them around and under the washer, this holds the thread from slipping back down into the mechanisms below the feed dog. I found that unlike the JUKI 1541S the Consew 255 with vertical axis has a bobbin that will spin like hell and cause all kinds of thread problems, bird nests and the like so I never sew without installing a starfish spring under the bobbin, this keeps the bobbin tight in the case and it will not spin.