Abstract: An angle trisecting device with a base section having two angle indicating scales and an elongated member with a straight edge portion. The elongated member is pivotally mounted on the base section. A given angle on one angle indicating scale coinciding with the straight edge portion corresponds to a trisected angle on the other angle indicating scale coinciding with the straight edge portion. Pivot pins extend from the elongated member and are removably captured in respective base slots to ensure reliable operation. In another embodiment a guide wall extends from the base to ensure reliable operation. An optional link arm is pivotally mounted to the base section and with one end pivotally mounted to the elongated member.