If order to get best performance from chisels and plane blades it is mandatory for them to be razor sharp. Sharpening requires a back and forth motion and when holding the tool without a guide, it's impossible to maintain the same angle during this motion and impossible to know what the bevel angle actually is. This easy-to-use guide attaches to the cutting tool and the sharpening angle can be easily determined. With a simple rolling motion razor sharp edges are gained. When using, keep firm pressure on the cutting edge and less on the roller thus minimizing stone wear. Creating precise secondary angles are also a snap. For chisels up to 1-5/8 in wide and plane blades up to 2-5/8 in wide.