OK safety stuff
wear safety glasses when making these pocket sized devices of havoc ... (i really need to come up with an official name for them)
be careful not to cut yourself when retrieving them
DO NOT FORGET TO TAKE THEM OUT OF YOUR POCKETS AT THE END OF THE DAY they go through the washer and well, its self explanitory

Step 1: Needed Items

a yard trimmer
metal file
at least one clamp (a vise will work)
hack saw, sawsall, or angle grinder with a cut off wheel
common sense (this is not optional)

Step 2: Get the Blades

take apart the trimmer and retrieve the 2 blades the bigger one is what these are made out of but as shown above the other one makes a nice bonus...

Step 3: Cutting and Shaping

i used my sawsall and cut a few of these things, clamped them to a stool and started filing away, actually first i tried using an angle grinder but it took off to much material too quickly and was hard to control on such a small piece, file as flat as you can otherwise it wont stick

Step 4: Throwing

grab it between your thumb and forefinger and throw it, if its not sticking you may have to re-shape it at a sharper angle, try practicing on a pop can for accuracy

P.S. BE CAREFUL with the "toothed sword thing" it can do more damage than you think