i’ve been hearing about this knife tool, and was woundering if any1 can tell me what it is.
just press k in a 2.3 blender window.
its a tool for editing meshes, like extrue.
It works on selected vertices. Select some, press k and cut the mesh.
It’s a kind of subdividing (I think). You could select two vertives, press w-subdivide and grab the new vertice to where you want and repeat this many time OR you can use the knife tool. 
k, thanx.