Join Date: Feb 2004
Location: beautiful coastal South Carolina
Bikes: 1991 Trek 930, 2005 Bianchi Eros, 2006 Nashbar "X," IRO Rob Roy
i think she means a "Shark Fin." it was a accessory from Shimano that claimed to reduce or eliminate chainsuck. it mounted on the drive side chainstay, with a "fin" near the crank and a flat part that ran along the stay. i've got one somewhere (had it on my Trek for years). it didn't work for s**t to prevent chainsuck, but it was a pretty neat looking chainstay protector. i doubt they've been made in years.
you can see one in this picture:
thanks to First Flight Bikes for the pic.
now there was a "Shark Tooth" accessory also - it mounted on the U-brake as an anti-jam device. but i've never seen one, and she'd have to flip the bike over to see it.