Binro the Heretic One of my first jobs was working at a place that made industrial air-handling and environmental control equipment.
One day, one of my coworkers was showing off a "homemade duck call" made from leftover materials. It consisted of a length of thin aluminum tubing coiled into a spiral with a fitting on one end that acted as the mouthpiece and a cone-shaped amplifier on the other end. He asked if anyone wanted to try it.
One young man volunteered. He took the device, drew a deep breath, pressed his lips to the mouthpiece and blew hard.
The guy standing behind him and to his left got a face full of blue chalk line dust.