The spine of the knife is the unsharpened section of the blade that faces the operator in the normal operation of a single bladed knife. On a double-edged knife, the spine is the swell in the centre of the blade, where the blade is thie thickest. The spine gives the knife its mechanical strength and allows a place to place extra leverage if need be. The spine may be augmented with jimping, filework, engraving etc. to increase its look and functionality.