TM 10-5411-232-13&P CARGO BED COVER (CBC) M105A2 TRAILER, TYPE II 0021 00 MAINTENANCE ALLOCATION CHART (MAC) Explanation of Columns in the Tools and Test Equipment Requirements - Continued Column (3) - Nomenclature.  Name or identification of tool or test equipment.   Column (4) - National Stock Number (NSN).  The NSN of the tool or test equipment. Column (5) - Tool Number.  The manufacturer’s part number, model number, or type number. Explanation of Columns in Remarks Column (1) - Remarks Code.  The code recorded in Column (6) of the MAC. 0021 00-4