Abstract: A chalk line assembly includes a housing formed with a cavity therewith to receive powdered chalk, with a chalk line wound within the housing about a central spool. A crank handle is directed into the housing to effect winding and reeling of a chalk line relative to the housing about the spool. A mounting plate is secured to a rear wall of the housing, with the mounting plate including a ferromagnetic member mounted to the mounting plate projecting rearwardly of the mounting plate. The mounting plate further includes a support aperture directed therethrough to receive fasteners permitting vertical mounting of the apparatus to ferrous and non-ferrous supports in directing a vertical chalk line. A modification of the invention includes a fiber optic housing structure mounted to the housing for projecting illumination and alignment with the chalk line and orthogonally oriented relative to the chalk line for measurement in a construction environment.