TM 10-3930-656-24P (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 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, 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., all authorized maintenance 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 0 -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  (designate  the  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