for complete versatility on the job. They are designed with interchangeable, replaceable, hardened tubular steel blades available in four diameters which can be exchanged to adapt to joint... size requirements. Wear is distributed during use by simply revolving the tubular steel blade. Should a blade eventually wear out, it is removed and a replacement installed... on thecast aluminum handle. The hardened tubular steel blades on both the Brick Jointers and Sled Runners produce a uniform and consistentlyfine finish on the mortar. No Tools Needed...