Rotary brushes are a popular attachment for pressure washers that can be used for a variety of cleaning tasks. They are typically used for more heavy-duty cleaning applications, such as removing stubborn dirt and grime from large surfaces like decks, patios, and sidewalks. Rotary brushes work by spinning rapidly and using the pressure from the water to scrub away dirt and debris, making them a highly effective cleaning tool. However, it's important to note that not all pressure washers are compatible with rotary brushes, so be sure to check your machine's specifications before purchasing one.