TM 10-3930-665-13&P (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 or aviation unit maintenance. O -Unit or aviation unit level 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. (b) The maintenance code entered in the fourth position tells whether or not the item is to be repaired and identifies the lowest maintenance level with the capability to do complete repair (i.e., perform all authorized repair functions).  (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.) This position will contain one of the following maintenance codes. CODE APPLICATION/EXPLANATION O -Unit or aviation unit is the lowest level that can do complete repair of the item. F -Direct support or aviation intermediate is the lowest level that can do complete repair of the item. H -General support is the lowest level that can do complete repair of the item. L -Specialized repair activity is the lowest level that can do complete repair of the item. D -Depot is the lowest level that can do complete repair of the item. 4