Start with angle PQR that we will bisect. 

1. Place the compasses' point on the angle's vertex Q. 

2. Adjust the compasses to a medium wide setting. The exact width is not important. 

3. Without changing the compasses' width, draw an arc across each leg of the angle. 

4. The compasses' width can be changed here if desired. Recommended: leave it the same. 

5. Place the compasses on the point where one arc crosses a leg and draw an arc in the
interior of the angle. 

6. Without changing the compasses setting repeat for the other leg so that the two arcs cross. 

7. Using a straightedge or ruler, draw a line from the vertex to the point where the arcs cross 

Done. This is the bisector of the angle ∠PQR. 
