Find a hacksaw blade. It does not matter wether it is new or used.
Step 2: Designing Your Knife
Draw the design you are going to use on the saw blade. Mark where the end of the blade will end, where the handle and blade meet, and the design of your blade. My blade will be 3.5in and my handle will be 4in. I am also using a simple "tanto" blade shape.
Step 3: Cutting Out Your Knife
Now get a hacksaw or dremel and cut out where you marked your blade.
Step 4: More Shaping And Sharpening
Now use a file or grinder to define the shape of your blade, remove saw teeth from the grip area, and sharpen you blades edge. Remember to always wear safety gear!
Step 5: Customization!
Now that the body of your knife is finished, feel free to add your own custom touches! I added jimping, cut another hole in the handle to make it easier to wrap, then I wrapped the tang with some shoelace. (I don't have any cord at the moment)