Definition of middle rail in English:

middle rail

noun

  • 1The rail of a door level with the hands, to which the handle or lock is usually fixed.

  • 2A third, cogged, rail between the two running rails of a railway line, used in connection with a rack-and-pinion device on an engine for the ascent and descent of steep inclines; (later also) an additional rail between the two running rails which conveys the current in some electric railways.

Origin

Late 17th century; earliest use found in Joseph Moxon (1627–1691), printer and globe maker.