(TrendHunter.com) It's commonplace for baristas to bang the espresso portafilter on a knock box to remove grounds between shot pulling which can cause fatigue and discomfort, so the ‘QuinSpin'... (TrendHunter.com) It's commonplace for baristas to bang the espresso portafilter on a knock box to remove grounds between shot pulling which can cause fatigue and discomfort, so the ‘QuinSpin'...