Don't EVER Do This!
I changed my foot from free-motion to the one for decorative stitches, set the stitch for an eyelet stitch, (thankfully I used the small test sandwich to try it out). Unfortunately, I forgot to raise the feed-dogs. Well, I thought I would never get that mess straightened out. The thread got into a huge, hard knot underneath the stitch plate. Finally I had to cut the sandwich off of the top of the jammed-in part, remove the foot, unscrew the stitch plate and cut the knot off. Don't ever do that.