TM 55-1680-317-23&P 2-7. SEWING REPAIRS- Continued Table 2-2.  Sewing Machine Code Symbols Code symbol Sewing Machine LD SEWING  MACHINE,  INDUSTRIAL  (Light  Duty):  General  sewing;  power  driven;  lock  stitch;  single needle; flat bed; with rigid table stand; 10- to 13-inches depth of throat; 31-15 or any equivalent model MD SEWING MACHINE, INDUSTRIAL (Medium Duty):  General sewing; power driven; lock stitch; single needle; flat bed; with rigid table stand; 111W155 or any equivalent model. DN SEWING MACHINE, INDUSTRIAL (Light to Medium Darning): Darning; power driven; lock stitch; single needle; 6-7/8-inches depth of throat; cylinder bed; with rigid table stand; 47W70 or any equivalent model. BT SEWING MACHINE, INDUSTRIAL(Light Duty): Bar tacking; with rigid table stand; 69-8 or any equivalent model. Table 2-3.  Stitching Specifications. Recommended sewing machine Component (code symbol) Stitches per Inch Thread size Individual Hot Climate Survival Kit Outer Case MD 7-9 FF DN Darn FF Grommet reinforcement MD 7-9 FF DN Darn FF Pocket tie tape MD 7-9 FF Carrying handle MD 7-9 FF Slide interlocking fastener MD 7-9 FF Inner Case MD 8-11 E Slide interlocking fastener MD 8-11 E Attaching strap MD 8-11 E Connecting strap MD 8-11 E Connecting strap reinforcement MD 8-11 E Tarpaulin LD 7-11 E First Aid Kit Case MD 8-11 E DN Darn E Tool Kit Carrier MD 7-11 FF Canned Drinking Water Test Pad LD 7-11 FF 2-28