TM 10-6640-215-13 B-2.  MAINTENANCE FUNCTIONS- continued g.   Remove/Install.    To  remove  and  install  the  same  item  when  required  to  perform  service  or  other  maintenance functions.    Install  may  be  the  act  of  emplacing,  seating,  or  fixing  into  position  a  spare,  repair  part,  or  module (component or assembly) in a manner to allow the proper functioning or an equipment or system. 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 serviceability 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  I  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 item group numbers are "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, see paragraph B-2). d. Column 4.  Maintenance Level.  Column 4 specifies, by the listing of a work time figure (expressed as man-hours shown as whole hours or decimals) in the appropriate subcolumn(s), the level 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  level  of  maintenance.    If  the  number  or  the  complexity  of  the  tasks  within  the  listed  maintenance function vary at different maintenance levels, appropriate work time figures will be shown for each level.  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 item    including    any    necessary    disassembly/assembly    time),    troubleshooting/fault    location    time,    and    quality assurance/quality control time in addition to the time required to perform B-2