Start with three line segments that will be the three sides of the triangle ABC. 

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

2. Set the compasses' width to the length of the segment AB.
This will become the base of the new triangle. 

3. With the compasses' point on A, make an arc near the future vertex B of the triangle. 

4. Mark a point B on this arc. This will become the next vertex of the new triangle. 

5. Set the compasses' width to the length of the line segment AC. 

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

7. Use the compasses to measure the length of the segment BC, the length of the third side of the triangle. 

8. From point B, draw an arc crossing the first. Where these intersect is the vertex C of the triangle 

9. Finally, draw the three sides AB, AC, and BC of the new triangle. 

10. Done. The blue triangle ABC has each side congruent to the the corresponding line segment. 
