TM 9-4120-411-24P (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 follow: Code Application/explanation PA Stocked items: use the applicable NSN to request/ PB requisition items with these source codes.  They are PC authorized to the level indicated by the code entered in the third position of the SMR code. PD PE PF PG NOTE: Items coded PC are subject to deterioration. KD Items with these codes are not to be requested/ KF requisitioned individually.  They are part of a kit which KB is authorized to the maintenance level indicated in the third position of the SMR code.  The complete kit must be requisitioned and applied. MO - Made at unit/AVUM Items with these codes are not to be requested/ level requisitioned individually.  They must be made from MF - Made at DS/AVIM bulk material which is identified by the part number in level the description and usable on code (UOC) column and MH - Made at GS level listed in the Bulk Material group of the repair parts list. ML - Made at Specialized If the item is authorized to you by the third position Repair Activity (SRA) code of the SMR code, but the source code indicates it MD - Made at Depot is made at a higher 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 the AF - Assembled by DS/AVIM assembled item must be requisitioned or fabricated and level assembled at the level of maintenance indicated AH - Assembled by GS by the source code.  If the third position code of the level SMR code authorizes you to replace the item, but the AL - Assembled by SRA source code indicates the item is assembled at a higher AD - Assembled by Depot level, order the item from the higher level of maintenance. XA - Do not requisition an “XA” coded item.  Order the next higher assembly.  (Refer to 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 by manufacturer’s part number. XD - Item is not stocked.  Order a XD-coded item through normal supply channels using CAGEC and P/N given, if no NSN is available. 2