Ground= the negative terminal of the battery is connected to the frame; all the negative (ground) sides of your circuits are connected to the frame which then connects through the frame metal back to the negative battery connection through its frame connection. Since the frames are usually bolted together in at least a few places to provide flexibility, the negative (ground) wires are usually run past these bolted joints to the same section of the frame that the battery negative is bolted to. This provides a better connection to complete the circuit without having to go through a bolted frame connection that is probably too loose to provide a good electrical connection and may even have a rubber bushing in it that will insulate or stop the circuit from completing.
The positive (hot) side of a circuit will always be connected to the other side of an electrical load (light, switch, coil, etc.) and not connected directly to the frame in any way. If the hot side of any circuit is connected in any way directly to the frame or negative (ground), then you have a dead short and it will blow a fuse or burn up a wire if no fuse is in the circuit (if the wire doesn’t melt in two or blow a fuse, it will drain the battery in a very short period of time).
I have attached a simple circuit which shows how you should wire your turn signal lights so that they will each only flash when the switch is turned one way or the other. Both will not flash at the same time in this circuit.
The turn signal switch has a terminal that is connected to both of the other terminals one at a time depending on the switch position (common terminal). The other 2 terminals are not connected to each other in any switch position. The common terminal should be wired to the flasher terminal not connected to the fuse. The other 2 terminals will be wired separately to each turn signal light.
