Johnny chock is the new, patented method for flushing out your black water tank. Johnny Chock allows for the continuous flow of water to your holding tank. When Johnny Chock is in place there is no need to hold or wedge toilet flush valve with your foot, hands or a stick. To use, simply open flush valve with hand or foot and place Johnny Chock in toilet bowl where it will keep valve open until you remove it. Also helpful when winterizing water system.