TM 10-3930-664-24 h. Replace.    To  remove  an  unserviceable  item  and  install  a  serviceable  counterpart  in  its  place.    "Replace"  is authorized by the MAC and is shown as the 3rd position code of the SMR code. i. Repair.  The application of maintenance services, including fault location / troubleshooting, removal / installation, and  disassembly  /  assembly  procedures,  and  maintenance  actions  to  identify  troubles  and  restore  service-  ability  to  an item by correcting specific damage, fault, malfunction, or failure in a part, subassembly, module (component or assembly), end item or system. j. Overhaul.  That maintenance effort (service / action) prescribed to restore an item to a completely serviceable / operational condition as required by maintenance standards in appropriate technical publications (i.e., DMWR).  Overhaul is normally the highest degree of maintenance performed by the Army.  Overhaul does not normally return an item to like- new condition. k. Rebuild.  Consists of those services / actions necessary for the restoration of unserviceable equipment to a like- new condition in accordance with original manufacturing standards.  Rebuild is the highest degree of material maintenance applied to Army equipment.  The rebuild operation includes the act of returning to zero those age measurements (hours / miles, etc.) considered in classifying Army equipment / components. B-3.EXPLANATION OF COLUMNS IN THE MAC, SECTION II. a. Column 1 - GROUP NUMBER.  Column 1 lists functional group code numbers,  the purpose of which is to identify maintenance  significant  components,  assemblies,    subassemblies,  and  modules  with  the  next  higher  assembly.    End group item number is "00". b. Column   2   -   COMPONENT   /   ASSEMBLY.      Column   2   contains   the   names   of   components,   assemblies, subassemblies, and modules for which maintenance is authorized. c. Column  3  -  MAINTENANCE  FUNCTION.    Column  3  lists  the  functions  to  be  performed  on  the  item  listed  in column 2.  For a detailed explanation of these functions, refer to paragraph B-2. d. Column 4 - MAINTENANCE LEVEL.  Column 4 specifies, by the listing of a work time figure in the appropriate sub-column(s), the category of maintenance authorized to perform the function listed in Column 3.  This figure represents the active time required to perform that maintenance function at the indicated category of maintenance.  If the number or complexity of the tasks within the listed maintenance function vary at different maintenance categories, appropriate work time figures will be shown for each category.  The work time figure represents the average time required to restore an item (assembly, subassembly, component, module, end item, or system) to a serviceable condition under typical field operating conditions.  This time includes preparation time (including any necessary disassembly / assembly time), troubleshooting / fault isolation time, and quality assurance / quality control time in addition to the time required to perform the specific tasks identified for the maintenance functions authorized in the maintenance allocation chart.  The symbol designations for the various maintenance categories are as follows: C Unit (Operator or Crew) O Unit Organizational Maintenance F Direct Support Maintenance H General Support Maintenance D Depot Maintenance B-2