angle sign, like the arrow sign, basically
means directed movement and is thus associated with energy. The
spectrum of meaning of this entry sign is centered around the concepts
effect. We see this
spectrum of meaning in , the sun rune in the earliest runic alphabet
(and a letter for s-sound in the Old Latin alphabet) and as in technical contexts and electricity notation.
In the ground-to-air emergency code, means mechanic is needed, i.e. something is wrong with the source of energy, the engine. In the British system of hobo signs, drawn on a wall denotes here they demand that you work hard.