Brushes are held in place by sliding through the slots in between the 'spring' at the top of the brush washer, which allows you to suspend the brush in your solvent or water, avoiding damage to the brush hairs if the brush is immersed in the washer for a considerable amount of time. The sediment accumulated from washing brushes sinks through the holes to the bottom of the washer pot, and helps keep your solvent cleaner for longer. When you need to clean or replace your solvent, decant what is in the washer into another vessel carefully, stopping just before the sediment starts to flow into the vessel, and then dispose of the sediment and clean/wipe the bottom of the pot before pouring the solvent back in and topping up with a little fresh solvent.