How signs help one read cues, and how they draw upon context to help make their meaning clearer.
Wet paint signs in many places tend towards either the hastily hand-written or just plain square. This one in Amsterdam gives a helpful cue in its form factor, drawing on the recognizable triangular “Caution” sign visible on so many European roads. Including the name of the company that produces the paint helps as well.
See also: signs in Yangon, Amman, Bangkok, and Chongqing – and how they draw upon (or are out of sync with) their surrounding context.