TM 9-2320-209-20-3-4 b. Replacement. FRAME 1 1. Slide duct (1) on heater adapter (2) and adapter (3). 2. Using wrench, tighten two capscrews (4). 3. Put strap (5) over duct (1) and aline screw holes. 4. Using wrench, screw in and tighten capscrew (6). END OF TASK 23-94