Knife tool in blender 2.57

Recently I heard someone advise this tutorial for character creation. I was looking through and saw this and noticed the knuckles. I learned that there was a knife tool so i tried replicating this but for some reason i can’t achieve it in blender 3d 2.57. If anyone has any suggestions or explanations it would help out alot. I can’t find anything like this from a simple google search on the internet.

edit mode -> select all (or the region you wish to slice) -> hold k -> drag through selection in the spot you wish to slice.

hope that helps!

The knuckles I selected the two verts on the top, used ‘V’ to rip, then moved them back - selected the two edges, ‘F’ for face, ctrl=R to loop cut, then selected the outside edges to make triangles with ‘F’. I think something similar could get you the beginning geometry of the nail area, since that would then allow you to extrude then.