ARMY TM 9-2815-252-24 AIR FORCE TO 38G1-92-2 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 I 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