How do I make cat-style claws for a werecat costume?

He, the character(it's for a movie) is mostly human, with catlike abilities. So he has claws for nails on his fingertips. But I'm not entirely sure how to do this. Something akin to Sabretooth's claws on X-Men.

fake nails...... they have really long ones at some places and you can paoint them watever color u want 
 someone already said that =( 
Get a set of glue-on fake fingernails from the beauty section of your local department store. Trim the nails so they just cover the actor's real nails, but not much longer. Use modeling clay to sculpt the shape of the cat claws on top of the fake nails. Coat the clay with a few layers of epoxy, Bondo, or other resin-type material and let cure. Remove the claw from the fake nail, scrape out the clay, trim, sand, & paint to taste. Glue the claw back onto the fake nail base with epoxy or super glue. Apply the claws to the actor using the nail glue supplied with the fake nails (or super glue gel, which is the same thing).

Alternately, they used to sell "paint-on" acrylic nails in the same section of the department stores, which was a kit with acrylic polymer and foil nail forms that let you paint the polymer resin directly onto your real nails and build out from there onto the foil forms. I don't know if they still sell those, but something like that might also work with a few mods to the foil forms.