Mnemonic comic for ⺊

Mnemonic symbol: ⺊ looks a bit like a pennant.

Someone stuck a flute into the middle of a hollow dinosaur bone to conduct studies on the speed of sound. At the one end of the hollow dinosaur bone is an answering pennant, used in the International Signal Code primarily for the reply "signal is received and understood", which should be raised as soon as the person is hearing the sound made by the flute.