Originally Posted by MadQuilter
The darning (or quilting) foot "rides" on the fabric, so it does not sit firmly on the fabric like a regular foot. You need to be able to move the fabric freely underneath the foot. However, you still need to bring the foot down with the lever as far as it will go. (I tried to do FMQ without the foot being engaged and the machine screamed at me. I didn't understand why because the foot LOOKED just fine.)
And some machines will make a big mess instead of "screaming" at you if you forget to lower the foot. Ask me how I know. lol