Start with the triangle ABC which we will copy.


1. Mark a point P that will be one vertex of the new triangle 

2. Set the compasses' width to the length of one side of the original triangle ABC. In this example we use AC. 

3. With the compasses' point on P, make an arc near where the next vertex of the triangle will be. 

4. Mark a point R on the arc. This will become the next vertex of the new triangle. PR is equal in length to AC 

5. Use the compasses to measure the length of the side AB in the original triangle. 

6.
Place the compasses' point on P and make an arc in the vicinity of where the third vertex
of the triangle will be.
All points along this arc are the distance AB from P,
but we do not yet know exactly where on this arc the the vertex is.


7. Use the compasses to measure the length of the side BC in the original triangle 

8. From point R, draw an arc crossing the first. where these intersect is the vertex Q of the triangle 

9. Finally, draw the three sides of the new triangle PQ ,PR, and QR. 

10. Done. The blue triangle PQR is congruent to the triangle ABC. 
