Use to create expressive lines on the XL Charcoal or Graphite blocks. Simply run the XL block along one of the 4 ridged sections to carve different grooves patterns in the block surface. Create "groovy" marks on paper with the Derwent Groove Cube. Just run your Derwent XL or any other Graphite and Charcoal Blocks along the edge of the Cube to create up to four indentations that play out beautifully on paper. You can also use it to shape the edges of charcoal and graphite blocks.