The hook knives you guys use kiting look all tiny and useless compared to the ones i use when i hang glide. We use the Jack Safety knife
www.moyes.com.au/file-not-foundWhich is about 25cm long and retails for about $30. Mine hasnt corroded yet, but i've never been unfortunate enough to have to use it. Although i guess it's a bit too big to tote around on your harnesses.. No specialised pockets or such.. Although I think they make a smaller version.
The ever stupid paragliders (i love them dearly, but why would ya do it?) have made up a whole page dedicated to hook knives, so if you want a bit of a read about them, head to:
www.paragliding-tales-and-reviews.com/paraglider-hook-knife.htmlOne last thing. Dont use your hook knife to cut bits of rope nad stuff, it's there to save your life and you want it to be as sharp as possible when you're in trouble. If you think it's getting a bit blunt, is $10-$30 too much to spend to replace a piece of equipment that could save your life?