The black squares are connection points, it means that the wires connect there. Where a wire (a line) goes straight thru another line its not connected to it.UNLESS, there's a black square!
The round dots and little black solid triangles (two per diagram only) are solder points also.The symbol that looks like 777 is a ground connection
I have been meaning to convert all these modified mustang schematics into simple diagrams for people for years, I just couldn't be bothered with it as they aren't that interesting mods IMO.
