TM  10-3930-669-20 15-22.  MAST ADJUSTMENT (CONT). NOTE • When   adjusting   the   inner   rail,   ensure   to   keep   the   same   amount   of   tension   on   both upper/secondary chains. • The distance from end of nut to end of shaft should be a minimum of 1/4 in.  (6 mm) on each side. (2)   To adjust inner rail (1), tighten or loosen nuts (4) on shafts (5) at rear top side of mast (2) until inner rail is even with center rail. (3)   Lower mast carriage (6) to the ground. (4)   Position  fork  (7)  to  the  far  right  of  the carriage  (6)  and  fork  (8)  to  the  far  left  of  the carriage. 15-78