Question

when color codes are not available, how can you identify where fuel gas lines connect to a torch body?
visible notches on the connection nut
right hand threads on the fuel gas connection
left had threads on the fuel gas connection
identifying marks such as an \o\ or an \f\

Explanation:

When color codes are unavailable, identifying marks like "O" (for oxygen) or "F" (for fuel gas) are standard ways to tell where fuel gas lines connect. Thread types (left - or right - hand) are more about assembly direction rather than identification. Visible notches on connection nuts are not a common identification method for fuel gas line connections.

Answer:

identifying marks such as an "O" or an "F"