Abstract: In a vertical lift for use in exterior locations to raise and lower a person, the lift comprising a support frame, a tower frame mounted on the support frame, a carriage secured to the tower frame so as to be vertically movable with respect thereto, a drive system associated with the tower frame to raise and lower the carriage between an upper and a lower position, and control means to enable a person using the lift to activate and deactivate the drive system as required, the improvement characterized in that the tower frame comprises a plurality of vertically extending guides secured to the tower frame and a carriage guide frame secured to the carriage and movably associated with the guides, and the drive system comprises a vertically oriented drive screw which, when activated, rotates in one direction to raise or in the opposite direction to lower a nut seated thereon so as not to rotate therewith, the guide frame supported by the nut for raising or lowering therewith.