SECTION I TM 9-2520-238-34P 3 Code Application/Explanation MO — Made at Items with these codes are not to be requested/            UM/AVUM level requisitioned individually. They must be made from bulk material which is identified by the MF — Made at part number in the DESCRIPTION AND USABLE ON            DS/AVUM level CODE (UOC) column and listed in the Bulk Material group of the repair parts list in this RPSTL. MH — Made at GS level If the item is authorized to you by the 3rd position code of the SMR code, but the source ML — Made at Specialized code indicates it is made at a higher level, order Repair Activity (SRA) the item from the higher level of maintenance. MD — Made at Depot AO — Assembled by Items with these codes are not to be requested/           UM/AVUM Level requisitioned individually. The parts that make up the assembled item must be requisitioned or AF — Assembled by fabricated and assembled at the level of           DS/AVIM Level maintenance indicated by the source code. If the 3rd position code of the SMR code authorizes you to AH — Assembled by replace the item, but the source code indicates           GS Category the item is assembled at a higher level, order the item from the higher level of maintenance. AL — Assembled by SRA AD — Assembled by Depot 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 CAGE 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 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  a  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 750-1. (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: