TM 10-4210-235-23P (1) Source Code.  The source code tells you how you get an Item needed for maintenance, repair, or overhaul of an end Item/equipment Explanations of source codes follow Code Explanation PA BB PC** PD PE PF PG Stocked Items, use the applicable NSN to request/requisition items with these source codes They are authorized to the category Indicated by the code entered in the 3d position of the SMR code. **NOTE   Items codes PC are subject to deterioration. KD KF KB Items with these codes are not to be requested/requisitioned individually.  They 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 org AVUM level) MF (Made at DS/AVUM level) MH (Made at GS level) ML (Made at Specialized Repair Activity (SRA)) MD (Made at Depot) Items with these codes are not to be requested/requisitioned individually.  They must be made 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 of the repair 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) AF (Assembled by DS/AVUM level) AH (Assembled by GS level) AL (Assembled by Specialized Repair Activity (SRA)) AD (Assembled by Depot) Items with these codes are not to be requested/requisitioned individually.  The parts that make up the assembled Item must be requisitioned or fabricated and assembled at the level of maintenance indicated at the source code.  If the 3d position code of the SMR code, authorizes you to replace the item, but the source code indicates the items are assembled at a higher level, order the Item from the higher level of maintenance. Code Explanation XA - - Do not requisition an "XA"-coded 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 FSCM and part number given. XC - - Installation drawing, diagram, instruction sheet, field service drawing, that is identified at manufacturer's part number XD - - Item is not stocked.  Order an "XD"-coded item through normal supply channels using the FSCM and part number given, rf 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 at requirements of AR 700- 42. 2