Choovie, The jib is the smaller sail at the front of the boat. There is a rope ( sailors call it a sheet) that attaches to the back of the jib. When the boat turns, you need to pull on that rope. The rope goes around a cylinder with a crank on it. Sailors call the cylinder a coffee grinder. Turning the crank to change the postion of the jib I would assume is what she means by grinding the jib.