Abstract: A brush includes a housing unit and a bristle plate disposed within the housing unit. The bristle plate has a plurality of parallel bristle elements projecting downward therefrom. A guide unit guides the bristle elements to move through the bristle holes of the housing unit. A resilient unit biases the bristle plate to move upward in the housing unit, so as to retract the bristle elements into the housing unit. A bristle-pushing member includes a generally inverted U-shaped body riding on the bristle plate, a rotating shaft provided on the body and journalled in the housing unit, a rotary lever connected securely to an end of the body, and a push lever connected securely to the other end of the body. Rotation of the rotary lever moves the bristle elements between an extension position and a retraction position.