what’s the knife tool and how do u use it?
It cuts selected Faces in Edit mode, get to it from K or Shft-K. Select an option, use LMB to mark your cuts and Enter to cut.
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Here : http://wiki.blender.org/index.php/Manual/Edge_and_Face_Tools#Knife_Subdivide
Although now when you hit K you also get the option for loop cutting as well as the options for the knife cut tool (ever since 2.42a actually) …You might want to look at the entire page of “Edge and Face Tools” as well as the page before that “Advanced Mesh Tools” and the page before and then the page after … The Wiki manual is still useful for the basics even if somewhat out of date … Or go read the release logs at Blender.org … The knife tool is documented for the 2.3x release I think as well as for other features/tools you might not be familiar with …