TM 9-2320-209-10-1 1. Depth of hole bored is checked through sighting holes (l, 2, and 3) in derrick tube (4). 2. When you can see bar guide (5) through sighting hole (1), bored hole is 8 feet deep. 3. When bar guide (5) reaches sighting hole (2), bored hole is 9 feet deep. 4. When bar guide (5) reaches sighting hole (3), bored hole is 10 feet deep. GO TO FRAME 8 4-344