In the cutting process, the hardie is the fixed tool that you place the material on and then strike with a hammer. The term "hardie" comes from the blacksmithing world. Traditional anvils have a square hole on one end for inserting various tools, including chisels. This hole is called a "hardy hole". The mosaicist's hardie looks just like a blacksmith's chisel. In Italian, this tool is called a "tagliolo", which actually means 'chisel".