Always raise your presser foot before threading your sewing machine or serger. Raising the presser foot opens the tension disks and allows the thread to go into the correct thread path. I realize this is Sewing 101 and a very basic tip, but many beginners don't have access to sewing lessons. (I didn't know to do this for years.) They may buy their machine online or in a Big Box store and never read their manual. Happy Sewing!