This project was inspired by a family I stayed with in Kenya. The only utensil they had was a sharpened butterknife shared by about twenty people.
Select your "blank":
Test your butterknives by bending the blade with your fingers. The farther you can bend it without it staying bent, the better it is.
Instead of a butter knife, you could use a saw blade or any piece of metal.
WARNING: I will be showing a bunch of OPTIONAL steps using tools.
For purist "no-tool" knifemaking, just skip all the steps using tools.
Or just substitute "with a rock" for the name of the tool.
Your knife will be fine.
Step 1: Optional: Drill Holes in Each End of the Handle
Skip this and the wrapping is the same and 95% as good.
Step 2: Optional: Countersink and Smooth the Holes
This will keep the burr on the edge of the hole from biting the cord or your hand.
Step 3: Optional: Melt and Taper the Cord End
Get your fingers wet so the melted plastic won't stick and burn you like napalm.
This is 1/8" nylon "parachute" cord. 1/8" Polyester is better because it doesn't get loose when wet. Get it at a chandler. (marine supply)
Step 4: Start Wrapping
If it's cotton or other cellulose fiber, make sure it's dry first.
Nylon shrinks when it dries, cotton shrinks when it's wet.
You don't really need the hole, that's just something to make it look less like a butter knife.
If you drilled holes poke the cord through one of the holes.
Leave a tail a few inches long.
If you skipped the hole just lay down the tail and wrap over it.
Wrap over the tail until you get halfway up the handle.