Remove the spray plate with the hex key & multi-tool. Remove the screws holding the brass shower head in place. Dislodge the shower head. Using the multi-tool latch onto the cartridge and dislodge from the shower column. Remove the fine mesh strainer from the cartridge and place under running water to remove any debris. Fit the strainer back on the cartridge & slot into the shower column. Replace and secure the shower head, insert the spray plate & screw into place.