SECTION I TM 10-3930-255-24P (1) Source Code.  The source code tells you how to get an item needed for maintenance, repair or overhaul of an end   item/equipment.      Explanations   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 3d 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.  They KB are part of a kit which is authorized to the maintenance category indicated in the 3d 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 A VUM 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 3d position code 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 mainten- ance. AO-(Assembled by Items with these codes are not UM/A VUM Level) to be requested/requisitioned individually.  The parts that AF-(Assembled by make up the assembled item DS/A VIM Level) must be requisitioned or fabric- ated and assembled at the level AH-(Assembled by of maintenance indicated by GS Category) the source code.  If the 3d posi- tion code of the SMR code by AL-(Assembled by authorizes you to replace the SRA) item, but the source  code indi- 2 AD-(Assembled cates the item is assembled at a by Depot) bled at a higher level, order the item from the higher level of maintenance. XA - Do not requisition an "XA"-coded Item.  Or- der 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 identi fied by the manufacturer’s part number. XD- Item is not stocked.  Order an "XD"- coded item through normal supply chan- nels 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, re- place and use the item.