TM 55-1560-307-13&P 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  3d  position code of the SMR code. i.  Repair.  The application of maintenance services', including fault location/troubleshooting2, removal/ installation,  and  disassembly/assembly  procedures3,  and maintenance   actions4   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 materiel 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-4.  FUNCTIONAL GROUPS (Section II, Columns 1 and 2).  The functional group shown in Section II, under columns 1 and    J 2, identify maintenance significant components, assemblies, and subassemblies with next higher assembly.  B-5.  MAINTENANCE FUNCTION (Section II,    Column 3).  Column 3 lists the functions to be performed on the items listed in column 2. B-6.        MAINTENANCE    CATEGORIES    AND    WORK TIMES   (Section   II,   Column   4).       The    maintenance categories  (levels)  AVUM,  AVIM,  and  DEPOT  are  listed on    the    Maintenance    Allocation    Chart    with    individual columns   that   include   the   work   times   for   maintenance functions    at    each    maintenance    level.        Work    time presentations such as "0.  1" indicate the average time it requires   a   maintenance   level   to   perform   a   specified maintenance   function.      If   a   work   time   has   not   been established,    the    columnar    presentation    shall    indicate "____.____"  Maintenance levels higher than the level of maintenance   indicated   are   authorized   to   perform   the indicated function. B-7.      TOOLS   AND   TEST   EQUIPMENT   (Section   II, Column  5,  and  Section  III).     Common   tool   sets   (not individual tools), special tools, test, and support equipment required to perform maintenance functions are listed alphabetically in Section III with a reference number to  permit  crossreferencing  to  column  5  in  the  MAC.    In addition, the maintenance category authorized to use the device is listed along with the item National stock number (NSN)   and,   if   applicable,   the   tool   number   to   aid   in identifying the tool/device. ¹Services  inspect,  test,  service,  adjust,  aline,  calibrate, and/or replace. ²Fault   locate/troubleshoot   the   process   of   investigating and detecting the cause of equipment malfunctioning; the act  of  isolating  a  fault  within  a  system  or  unit  under  test (UUT). ³Disassemble/assemble   encompasses   the   step-by-step taking  apart  (or  breakdown)  of  a  spare/functional  group coded item to the level of its least componency identified as  maintenance  significant  (i.e.,  assigned  an  SMR  code) for the category of maintenance under consideration. ⁴Actions welding, grinding, riveting, straightening, facing, remachining, and/or resurfacing. B-4