An American National Standard. Approved December 2, 2009 American National Standards Institute (ANSI), A reaffirmation of MH27.2 – 2003. 33p. This specification apply to underhung cranes whose end trucks operate on the lower flange of a patented-track runway section; and to carriers (trolleys) operating on single-track patented-track monorail systems, including all curves, switches, transfer devices, lift and drop sections, and associated equipment.