ARMY TM 9-2815-255-24 AIR FORCE TO 38G1-95-2 MARINE CORPS TM 2815-24/4 d. Column  4  Maintenance  Category.    Column  4  specifies,  by  the  listing  of  a  work  time  figure  in  the  appropriate subcolumn(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 varies 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    location    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 Operator or Crew O Unit Maintenance F Direct Support Maintenance H General Support Maintenance D Depot Maintenance e. Column 5 - Tools and Equipment.  Column 5 specifies, by code, those common tool sets (not individual tools) and special tools, TMDE, and support equipment required to perform the designated function. f. Column 6 - Remarks.  This column shall, when applicable, contain a letter code, in alphabetic order, which shall be keyed to the remarks contained in section IV. B-4.  EXPLANATION OF COLUMNS IN TOOL AND TEST EQUIPMENT REQUIREMENTS, SECTION III. a. Column  I  -  Reference  Code.    The  tool  and  test  equipment  reference  code  correlates  with  a  code  used  in  the MAC, section II, column 5. b. Column  2  -  Maintenance  Category.    The  lowest  category  of  maintenance  authorized  to  use  the  tool  or  test equipment. c. Column 3 - Nomenclature.  Name or identification of the tool or test equipment. d. Column 4 - National Stock Number.  The National stock number of the tool or test equipment. e. Column 5 - Tool Number.  The manufacturer's part number. B-5.  EXPLANATION OF COLUMNS IN REMARKS, SECTION IV. a. Column 1 - Reference Code.  The code recorded in column 6, section II. b. Column 2 - Remarks.  This column lists information pertinent to the maintenance function being performed as indicated in the MAC, section II. B-3