Knowledge of pencils
Tips for sharpening a pencil with a knife
In order to cut the blade as hard as possible, it is better to use the front of the blade to cut only the wood first, and then use the original blade to make the blade stand and cut the core.
The point of how to use a finger is to use the thumb of a hand holding a pencil. You can cut well if you push the back of the blade while licking the blade.