Switchblade Combs on wikipedia.org

These were folding pocket combs with a handle that looked just like the classic stilleto switchblade knife, with the spring release button and even a slide safety button just like the real thing. A lot of 70's comic books have at least one ad for these novelty items, and even an episode of Happy Days saw The Fonz with one. They are still sold over the net and at flea markets, but were most popular ine the 1970's, they were very "70's cool."