SECTION I TM 9-2350-277-24P (1) Source  Code.    The  source  code  tells  you  how  to get  an  item  needed  for  maintenance,  repair  or  overhaul  of an end item/equipment.  Explanation of source codes follows: Code Application/Explanation PA Stocked items; use the applicable NSN to PB request/requisition items with these PC** source codes.  They are authorized to the PD category indicated by the code entered in PE 3rd position of the SMR code. PF PG ** Items coded PC are subject to deterioration. KD Items with these codes are not to be KF requested/requisitioned individually. KB They are part of a kit which is authorized to the maintenance category indicated in the 3rd position of the SMR code.  The complete kit must be requisitioned and applied. MO - (Made at UM Items with these codes are not AVUM Level) to be requested/requisitioned MF - (Made at DS/ individually.  They must be made AVUM Level) from bulk material which is identified by the part number in the DESCRIPTION AND USABLE ON CODE (UOC) column and listed in the Bulk Material group ML - (Made at of the repair parts list in this Specialized Repair RPSTL.  If the item is authorized Act (SRA)) to you by the 3rd position of the SMR code, but if the MD - (Made at source code indicates it is made Depot) at a higher level, order the item from the higher level of mainte- nance. AO - (Assembled by Items with these codes are not UM/AVUM Level) to be requested/requisitioned individually.  The parts that AF - (Assembled by make up the assembled item DS/AVIM Level) must be requisitioned or fabricated and assembled at the level AH - (Assembled by of maintenance indicated by GS Category) the source code.  If the 3rd position of the SMR code AL - (Assembled authorizes you to replace the SRA) item, but the source code AD - (Assembled by indicates the item is assembled Depot) at a higher level, order the item from the higher level of mainte- nance. XA - Do not requisition an "XA" - codes Item. Order its next higher assembly.  (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 the 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  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   items.      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: Code Application/Explanation C Crew or operator maintenance done within unit or aviation unit maintenance O Unit maintenance or aviation unit category can remove, replace and use the item. F Direct support or aviation intermediate level can remove, replace and use the item. H General support level can remove, replace and use the item. L Specialized repair activity can remove, replace and use the item. D Depot level can remove, replace and use the item 2