TM 10-4320-346-12&P (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: Source Code Explanation PA Stocked items; use the applicable NSN to request/requisition items with these PB source codes.  They are authorized to the category indicated by the code PC** entered in the 3rd position of the SMR code. PD PE **NOTE: Items coded PC are subject to deterioration. PF PG KD Items with these codes are not to be requested/requisitioned individually.  They KF are part of a kit which is authorized to the maintenance category indicated in the KB 3rd position of the SMR code.  The complete kit must be requisitioned and applied. MO - (Made at Unit/AVUM Level) Items   with   these   codes   are   not   to   be   requested/requisitioned individually.  They must be made from bulk material which MF - (Made at DS/AVUM Level) is identified by the part number in the DESCRIPTION and USABLE ON CODE (UOC) column and listed in the Bulk MH - (Made at GS Level) Material group of the repair parts list in this RPSTL.  If the ML (Made at Specialized item is authorized to you by the 3rd position code of the SMR Repair Activity (SRA)) code, but the source code indicates it is made at a higher MD - (Made at Depot) level, order the item from the higher level of maintenance. AO - (Assembled by Unit/AVUM Items with these codes are not to be requested/ Level) requisitioned individually.  The parts that make up AF - (Assembled by DS/AVIM the assembled item must be requisitioned or Level) fabricated and assembled at the level of AH - (Assembled by GS maintenance indicated by the source code.  If the Category) 3rd position code of the SMR code authorizes you AL - (Assembled by SRA) to replace the item, but the source code indicates AD - (Assembled by SRA) the items are assembled at a higher level, order the (Assembled by Depot) item from the higher level of maintenance. XA - Do not requisition "XA"-coded item.  Order its next higher assembly.  (Refer to the NOTE below.) XB - If an "XB" item is not available from salvage, order it using the CAGEC and part number given. XC - Installation drawing, diagram, instruction sheet, field service drawing, that is identified manufacturer's part number. XD - Item is not stocked.  Order an "XD"-coded item through normal supply channels using the CAGEC and part number given ,if no NSN is available. C-2