Most track hubs are spaced at 120mm and have either fixed threading on both sides (for a cog & lockring) or are fixed on one side with threads for a common freewheel on the other. You can install a freewheel on fixed threading but you cannot install a cog and lockring on freewheel threading.

When putting a track hub on a road frame spaced at 130mm, you need to use a 5mm axle spacer on each side.