I've never heard there were such things. They have symbols??? I won't go to the link...but some have mentioned triangles. When I was young those would bring to mind geometry, geodesic domes, and Old West chuck-wagons (the cook would clang or "ring" a triangle when the food was done). Oh --- and the Bermuda Triangle where boats and planes just disappear...
and small double triangles for the Cascade Cartridge Company. CB caps used to be fun...ploink.
similar to wearing an earring in your left ear for homosexual men identifying ea other