This picture shows examples of three Tridacna shell adzes and a gouge. The cutting edges on shell adzes were made in several different shapes. Some blades have straight edges with a single bevel from one side. Some are "beaked" or pointed at the center of the cutting edge. Other examples have a rounded cutting edge. The gouge in the center of this picture has a rounded cutting edge and it's sharpened by hollowing out more of the center which gives it a U-shaped cross section. The large adze at the left measures 3 9/16 inches (9 cm) wide.