Cob roller is a tool used for smoothing cob in construction of buildings. Although the term "cob roller" is widely used, it has several synonyms that can be used in its place, depending on regional and cultural variations. In the United Kingdom, the tool is referred to as a treader or treading board. In the United States, it is also known as a cob tamper or cob stamper. Additionally, it can be called a rammer, a compactor, or a roller. While the word "cob" is specific to the building material itself, its accompanying tool can have various names, all of which serve the same purpose.