If you are indeed talking about the kung fu weapon, they are also called crescent moon blades/knives, hook swords, deer horn knives, or mandarin duck blades. As far as I know they are only used in the Bagua/Pakua style. I have seen a few different forms for these, I have a few on VCDs imported from China, and there are great resources available at YMAA.com This book on Emei Baguazhang is fabulous and has a chapter on the weapon. http://store.yahoo.com/ymaa/bagandap.html And there is a companion video series, volume 3 has the hook sword forms and applications. They even have a video clip you can watch. http://store.yahoo.com/ymaa/embagvol3bag.html