Knock boxes are handy to have and easy to use. Knockboxes are used to 'knock out' to the spent ground coffee out of the portafilter (filter handle) so the next espresso can be prepared. Turn your portafilter upside down and give it a good smack against the inner bar or side of the box to loosen the spent espresso puck. Keep the mess in the box, and the flavor in the cup. The knockbox should be cleaned minimum once per day or when full.