A blackboard eraser including a cube having two semi-cylindrical grooves symmetrically
arranged in a longitudinal direction therein, and a central brush atop an elevated
surface formed between the two grooves. A longitudinal groove is defined underneath
each of the send-cylindrical grooves, and equal-length side brushes, which are
affixed to an inner surface of a lid, are respectively positioned in the longitudinal
grooves. Two grooves are arranged adjacent to each end of the semi-cylindrical
grooves, which provide for a shaft affixed to each end of a roller to dispose therein.
The brushes and the rollers form the eraser, which are enclosed within a closed
chamber between the lid and the two semi-cylindrical grooves. When erasing chalk
dust from a blackboard, the chalk dust sticks to the rollers and is carried to
the side brushes. The side brushes then wipes the dust, which falls into the closed chamber.
