Grab the end of the spark plug wire where it connects to the spark plug of your Ryobi 31CC weed whacker. Pull the wire off the spark and place the Ryobi on its side.
Hold the outer spool housing in one hand. Turn the bump knob on the bottom center of the attachment clockwise with your free hand. If necessary, use a pair of pliers to turn the bump knob.
Remove the bump knob from the attachment. Continue holding the outer housing and grab the edges of the inner spool with your free hand.
Pull the inner spool out of the outer housing. The string attachment is now open for winding new string and cleaning inside the housing.