I would use Cetol on any surface that you need traction like ladders,
wood dink floors, etc. That being said, the teak decks on my boat are
just plain, no finish whatsoever. For rails and brightwork that you
want to look nice but not walk on, I use Honey Teak by Signature
finish. VERY durable and pretty but a little hard to put on the first
time. Follow the directions exactly. After that, just a coat or two of
clear every 12-18 months is fine. http://www.fabulainc.com/ It's a
polyurethane, BTW.