TM 9-2815-250-24&P B-2. MAINTENANCE FUNCTIONS (continued). f. Calibrate.    To  determine  the  accuracy  of  and  cause  corrections  or  adjustments  to  be  made  on  instruments  or test,  measuring,  and  diagnostic  equipment  (TMDE)  used  in  precision  measurement.    Calibration  consists  of comparisons of two instruments, one of which is a certified standard of known accuracy, to detect and adjust any discrepancy In the accuracy of the instrument being compared. 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 of an end Item 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  third  position  of  the  source,  maintenance,  and  recoverability  (SMR) code. i. Repair.      To    apply    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 any specific damage, fault, malfunction, or failure in a part, subassembly, module (component or assembly), end Item, or system. j. Overhaul.    To   perform   that   maintenance   effort   (service/action)   required   to   restore   an   item   to   a   completely serviceable/operational  condition  as  required  by  maintenance  standards  in  an  appropriate  technical  publication (e.g., depot maintenance work requirement).  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.    To  perform  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 (e.g., hours, miles) considered In classifying Army equipment/components. B-3. EXPLANATION OF COLUMNS IN SECTION II, MAINTENANCE ALLOCATION CHART FOR ENGINE ASSEMBLY, DIESEL, HATZ 2 G 40. a. (1) Group Number.   Column  1  lists  functional  group  code  numbers,  whose  purpose  is  to  identify  maintenance- significant  components,  assemblies,  subassembies,  and  modules  with  the  next  higher  assembly.    The  end  Item group number is "00." b. (2)  Component/Assembly.    Column  2  contains  the  names  of  components,  assemblies,  subassemblies,  and modules for which maintenance is authorized. c. (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 para B-2.) d. (4) Maintenance Level.  Column 4 specifies, by the listing of a work-time figure 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 complexity  of  the  tasks  within  the  listed  maintenance  function  varies  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    time    (including    any    necessary disassembly/assembly B-2