Any question answered...

Q
Sheldon mentions using two cogs on a flip-flop hub. How is this achieved?

by screwing one on either side

from internet:
[INDENT]I have a 15t on my freewheel side with a bottom bracket lockring for insurance. I would not run this on the street, but it is fine for the track. The rental bikes at the track just have a cog screwed on the freewheel side.[/INDENT]
why OK for the track but not the street? stopping/ skidding?

Twin fixed? You can use a lockring that is on the same thread as cog.

doesn't a lockring threaded the same direction as a cog defeat the purpose...

Only if you want death in the face that is.

...hence the above comment?

Lynx, anyone that can give an appropriate answer deserves a gold star in telepathy.

how can i clarify? x