Big Horn 19640 Rotape Beam-Compass. Draw circles from 2 13/16" to 79" radius. To use: insert pin thru center hole in tape body and place at center of radius to be drawn.
Insert pencil (included) through hole in tape end. Adjust tape to required radius and draw. To draw parallel lines, slide straight edge on back of body along edge of material with one hand while guiding tape end & pencil with other.