TM 5-4220-231-14&P Source  Code Explanation PA Stocked  items: use  the applicable  NSN or manufacturers partnumber PB to   request/requisition   items   with  these     source    codes. They   are PC authorized  to the  category   indicated  by the  code   entered   in the 3d PD PE position of the  SMR code. PD PG KD Items with these codes are not to     be requested/requisitioned KF individually. They    are    part   of  a   kit  which     is  authorized to   the   mainte- KB nance category indicated in  the    3d    position of   the    SMR    code. The complete kit  must    be    requisitioned and    applied. MO-(Made at   org/AVUM Level) Items with these codes are not to     be requested/requisitioned MF-(Made at   DS/AVUM Level) individually. They     must    be   made    from    bulk   material    which     is  identified MH-(Made at  GS    Level) by  the    part   number in  the    DESCRIPTION AND     USABLE ON   CODE ML-(Made at  Specialized Repair     Act   (SRA)) (UOC) column and     listed in  the     Bulk     Material group of   the    repair MD-(Made at   Depot) parts    list    in  the    RPSTL. If  the    item    is   authorized to   you     by   the    3d position code of   the    SMR    code, but   the    source code indicates it  is made at    a    higher level, order the     item     from    the     higher level     of maintenance. AO-(Assembled by  org/AVUM Level) Items with these codes are not to     be requested/requisitioned AF-(Assembled by   DS/AVUM Level) individually. The     parts     that    make up   the    assembled item    must     be AH-(Assembled by   GS    Category) requisitioned or  fabricated and   assembled at  the   level    of  maintenance AL-(Assembled by   SRA) indicated by   the    source code. If  the    3d    position code of   the    SMR AD-(Assembled by   Depot) code authorized you    to   replace them,     but   the   source code indicates the    item     is    assembled at    a    higher level, order the    item    from    the higher     level    of   maintenance. XA Do   not   requisition an   "XA"-coded item.     Order    its   next    higher    assem- ^bly.(Also,     refer   to   the    NOTE     below.) XB If an   "XB"  item   is  not   available from   salvage, order    it  using    the   CAGE and    part   number     given. XC Installation drawing, diagram, instruction sheet, field   service drawing, that   is   identified by   manufacturer's part   number. XD Item    is    not    stocked. Order an    "XD"-coded item    through normal supply channels using    the    CAGE     and    part   number given, if  no   NSN is   available. NOTE Cannibalization or  controlled exchange, when    authorized, may    be   used as    a   source of   supply for   items     with   the    above source codes, except for   those source coded "XA"  or   those aircraft    support items     restricted by   requirements of   AR   700-42. (2) Maintenance Code. Maintenance codes tell   you    the   level(s) of   maintenance authorized to   USE and    REPAIR support item. The    maintenance codes are    entered in  the   third   and    fourth    positions of  the   SMR    Code as   follows: (a) The     maintenance code entered in  the   third   position tells    you    the    lowest maintenance level authorized to   remove, replace, and    use    an   item. The    maintenance code entered in  the   third   position will   indicate authorization to   one    of  the    following levels of   maintenance: E-2