TM 10-3930-659-20 17-11.    CARRIAGE ASSEMBLY REPLACEMENT (Con't). WARNING Use extreme caution when handling heavy parts.  Lifting device Is required  when  parts  weigh  over  50  lb  (23  kg)  for  a  single  person lift, over 100 lb (45 kg) for a two person lift, and over 150 lb (68 kg) for a three or more person lift.  Keep clear of heavy parts supported only  by  lifting  device.    Failure  to  follow  this  warning  may  cause serious Injury or death to personnel. 10. Attach  suitable  lifting  device  to  backguard  (3) and position backguard on carriage (8). 11. Install  backguard  (3)  on  carriage  (8)  with  four washers (6), screws (7), and new locknuts (9). 12. Remove lifting device from backguard (3). 13. Install three spacers (4), washers (2), screw (1), and new locknut (5) on backguard (3 . FOLLOW-ON TASKS: • Install forks (see paragraph 17-12). • Install fork spacing cylinder (see paragraph 17-33). TA707638 17-38