From the Southwest Ceramic Typology Project: Chaco PIII Corrugated as defined here is characterized by rim sherds with indented or clapboard exterior corrugations exhibiting a rim eversion greater than 60 degrees (Reed and others 1998). This type is characterized by the range of rim eversion originally utilized to define Mesa Verde Corrugated for the Northern San Juan tradition. This pottery first occurs in assemblages dating to the twelfth century and is most common at those dating to the thirteenth century. Only rim sherds were assigned to this type as body sherds were assigned to descriptive types based on characteristics noted for coils.