FOUR YEARS UNDER DEVELOPMENT! Patent No: US 9,259,740 B1 The High-Low Riffles have a scraping action on the bottom layers enhancing gold recovery. The pin design operates like a rake, settling heavy material to the bottom. Designed to open up channels for gold to fall down. The pins transfer vibration to upper levels of material being processed. For use only in our Large Royal Gold DryWasher, designed to open up channels for gold to fall down.