A head knife is one of those tools that pretty much only a leatherworker would have. Simply described, it is a half-circle blade with a handle on it. Extremely sharp, it is a potentially dangerous tool to use. I have not yet become accustomed to using it, partially for fear of cutting my hand off, partially because I am comfortable using my X-acto knife. I know it is very versatile and useful, but I just haven't yet got the knack for using it.