I'll now show you how to make a little knife for carving in bark, you can't carve wood with it, but it is the best thing i have ever used for making a bark boat. it is a very easy knife, toked me about 20 minutes to do.

Step 1: Getting the Blade

The first step is to get a thin piece of metal. this is a street sweeper bristle You can find metal pieces like this lying on the street beacose.
they fall/break off the scrubber brushes on the bottom of the street sweeper as it cleans the roads. but every hard, long, thin iron piece will do fine.

Step 2: Sharping the Blade

Well i guess you already know what to do; sharping the blade, this metal is very easy to get razor sharp in no time. sharp it from the top and about three centimeters down. sharp it on both sides.

Step 3: Handle

get a piece of wood, about one centimeter thick and 10 centimeters long. drill a hole on the top of it. the radius should be a about 0,1 millimeter smaller then the metal piece.

Step 4: Inserting in the Blade in the Handle.

gently hammer the blade down in the handle until it's 2 to 1,5 centimeters of the blade is left. bend it in a "U" shape.
Cut i very thin piece of leather and poke it down in the gap between the blade and the handle.
then cut the rest of the leather away. This will make the blade more stable.