TM 10-3930-671-24 b. Installation. WARNING Use  care  when  removing  or  installing  snap  and  retaining  rings.    Snap  and  retaining  rings  are under spring tension and can act as projectiles when released and could cause severe eye injury. (1) Install two chain roller sheaves (11) on lift chain sheave carrier (8) with two snap rings (12). (2) Install two chains (3) and guard (9) on two lift chain sheaves (11) with two screws (10).  Tighten screws 55-60 lb-ft (75-81 N•m). (3) Install  hose  sheave  assembly  (7)  and  bracket  (6)  on  lift  chain  sheave  carrier  (8)  with  two  screws  (5).    Tighten screws 55-60 Ib-ft (75-81 N•m). (4) Start engine (TM 10-3930-671-10). (5) Apply tension to two chains (3) and remove blocks from under carriage (2) and mast inner rail (1) (TM 10-3930- 671-10). (6) Install backrest on carriage (Para 5-24). END OF TASK 5-48