TM 5-4310-451-24P Code Application/Explanation PA Stocked items; use the applicable NSN to PB request/requisition items with these source PC** codes.  They are authorized to the category PD Indicated by the code entered In the 3d PE position of the SMR code. PF **  Items  coded  PC  are  subject  to PG deterioration. Items with these codes are not to be KD requested/requisitioned  individually.  They KF are part of a kit which is authorized to the KB 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 to AVUM Level) be requested/requisitioned MF-(Made at DSI individually.  They must be made AVUM Level) from  bulk  material which  is MH-(Made at GS identified by the part number In Level) the DESCRIPTION AND USABLE ON CODE (UOC) column and ML-(Made at Spe- listed in the Bulk Material group cialized Repair    of the repair parts list in this Activity (SRA)) RPSTL.  If the item is authorized MD-(Made at to you by the 3d position code of Depot) the SMR code, but the source code indicates it is made at a higher level, order the item from the higher level of maintenance. Items with these codes are not to be requested/requisitioned AO-(Assembled by    Individually.  The parts that make UM/AVUM up the assembled item must be Level) requisitioned or fabricated and AF-(Assembled by assembledatthe  level  of DS/AVIM maintenanceindicted by the Level) source code.  If the 3d position AH (Assembled by code of  the SMR code GS Category) authorizes you to replace the item,  but  the  source  code AL-(Assembled by indicates the item is assembled SRA) at a higher level, order the item AD-(Assembled by    from the higher level  of Depot) maintenance. X4 - Do not requisition an "XA"-coded item.  Or- der its next higher assembly.  (Also refer to the NOTE following.) 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 the 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 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 en- tered 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 indi- cate authorization to one of the following levels of maintenance. Code Application/Explanation C - Crew or operator maintenance done within unit maintenance or aviation unit mainte- nance. 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. D- Depot level can remove, replace, and use the item. (b) The maintenance code entered in the fourth position tells whether or not the item is to be re- paired and identifies the lowest maintenance level with the capability to do complete repair (i.e., perform all authorized repair functions).  (NOTE: Some limited re- pair may be done on the item at a lower level of maintenance, if authorized by the Maintenance Alloca- tion Chart (MAC) and SMR codes.) This position will contain one of the following maintenance codes: Code Application/Explanation O - Unit maintenance or aviation unit is the low- est level that can do complete repair of the item. F - Direct support or aviation intermediate Is the lowest level than can do complete repair of the item. 2