TM 55-1680-358-12&P 2-9. System Installation - Ramp .  Install the ramp as follows: a.  Installation Preparation.  Extend the ramp tongue to gain access to the four screws that attach the center skid pad (Figure 2-12). NOTE Step     2-9a.(1)     will     require     two persons.  Also, it requires that the screw  heads  be  fully  cleaned  of any  dirt,  etc.,  in  order  to  prevent slippage    due    to    the    awkward position. (1)    One  person  must  clean  screw  heads  and hold  the  screwdriver  (Figure  2-13)  while  resting  on  the ramp floor.  At the same time, the second person must be  under  the  ramp  using  a  suitable  wrench  to  remove the   nuts   securing   the   center   skid   pad.      Retain   the hardware   removed   for   reuse   during   the   installation procedure. (2)  Refer to Figure 2-14.  Remove fifteen bolts shown from the outboard left side of the helicopter ramp floor.    These  locations  will  be  used  to  secure  left-hand ramp   guide   rail/roller   assembly   (7,   Figure   3-2)   and transition   roller   assembly   rest   plate   (25).      Place   the removed bolts in storage. (3)        Refer    to    Figure    2-14.        Remove    the symmetrically opposite fifteen bolts located on the right side of the helicopter ramp floor.  These locations will be used     to     secure     right-hand     ramp     guide     rail/roller assembly  (8,  Figure  3-2)  and  transition  roller  assembly rest plate (25).  Also place the removed bolts in storage. (4)    Refer  to  Figure  2-15.    Remove  12  bolts shown  from  the  left  center  area  of  the  helicopter  ramp floor.    These  locations  will  be  used  to  secure  left-hand inboard  ramp  roller  assembly  (13,  Figure  3-2)  and  one end    of    forward    ramp    center    roller    mounting    bar assembly  (16)  and  aft  ramp  center  roller  mounting  bar assembly (17).  Place the removed bolts in storage. (5)        Refer    to    Figure    2-15.        Remove    the symmetrically   opposite   12   bolts   located   in   the   right center    area    of    the    helicopter    ramp    floor.        These locations will be used to secure right-hand inboard ramp roller assembly (14, Figure 3-2) and one end of forward ramp  center  roller  mounting  bar  assembly  (16)  and  aft ramp  center  roller  mounting  bar  assembly  (17).    Place the removed bolts in storage. NOTE Figure  2-16  illustrates  the  system components and the ramp extension components to be installed  on  the  helicopter  ramp. Also, refer to Figure 2-17, 2-18 and 2-19   for   locations   to   install   the bolts removed during aircraft preparation   (para   2-9),   securing these components. b.    Left-  and  Right-Hand  Ramp  Guide  Rail/Roller Assemblies.      Install   left-hand   Install   left-hand   ramp guide rail/roller assembly (7, Figure 3-2) and right-hand ramp guide rail/ roller assembly (8) as follows: (1)  Position left- and right-hand ramp guide rails (12,  Figure  3-6)  on  B.L.    41.577  (10  bolts)  and  B.L. 41.432 (two bolts) (Figure 2-17).  Make sure that the bolt holes  are  aligned  with  the  holes  from  which  bolts  were removed in Figure 2-14. (2)  Attach left- and right-hand ramp guide rails  (12,  Figure  3-6)  to  the  helicopter  ramp  floor.  Use one hex head bolt (32, Figure 3-2) and one flat washer (33)  at  the  most  forward  bolt  location  on  each  ramp guide rail along B.L.  41.432. (3)  Secure left- and right-hand ramp guide rails (12, Figure 3-6) at the remaining bolt locations.  Use 11 hex  head  bolts  (30,  Figure  3-2)  and  flat  washers  (31, Figure 3-2). (4)        Position    transition    roller    assembly    rest plates  (25)  on  the  three  holes  located  at  or  near  B.L. 32.026 on each side of the helicopter ramp.  Secure the rest plates to the floor.  Use six countersunk bolts (34). Fit  bolts  loosely  before  tightening.    Use  three  bolts  per pad. c.    Forward  and  Aft  Ramp  Center  Roller  Mounting Bar   Assemblies.      Install   forward   ramp   center   roller mounting  bar  assembly  (16,  Figure  3-2)  and  aft  ramp center roller mounting bar assembly (17) as follows: (1)    Position  forward  and  aft  ramp  center  roller mounting  bar  assemblies  (16,  and  17,  Figure  3-2)  on B.L.    17.587  (Figure  2-18)  over  the  bolt  locations  from which bolts were removed (para 2-9a.(4) and 2-9a.(5)). (2)    Secure  forward  and  aft  ramp  center  roller mounting  bar  assemblies  (16  and  17)  to  the  helicopter ramp   floor.      Use   four   hex   head   bolts   (38)   and   flat washers (31). 2-19