TM  10-3930-657-24P 3. Explanation of Columns (Sections II and Ill) (Con’t). 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. (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: (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 indicate authorization to one of the following levels of maintenance. Code Application/Explanation c - Crew or operator maintenance done within unit maintenance or aviation unit maintenance. O - Unit maintenance or aviation unit 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, replace, and use the item. D - Depot level can remove, replace, and use the item. NOTE Some limited repair may be done on the Item at a lower level of maintenance, if authorized by the Maintenance Allocation Chart (MAC) and SMR codes. (b) The maintenance code entered in the fourth position tells whether or not the item is to be Code o F H L D z B repaired and identifies the lowest maintenance level with the capability to do complete repair (i.e., perform all authorized “Repair” functions). This position will contain one of the following maintenance  codes: Application/Explanation - Unit maintenance or aviation unit is the lowest level that can do complete repair of the item. - Direct support or aviation intermediate is the lowest level than can do com- plete repair of the item. - General support is the lowest level that can do complete repair of the item. - Specialized repair activity is the lowest level that can do complete repair of the item. - Depot is the lowest level that can do complete repair of the item. - Nonreparable, No repair is authorized. - No repair is authorized, (No parts or special tools are authorized for the maintenance of a “B”-coded item.) However, the item may be recondi- tioned by adjusting, lubricating, etc., at the user level. 3 Change 1