How to Make an Equilateral Triangle Using a Compass
It is time to learn how-to construct an equilateral triangle using a bar compass.

Remember, the length of each of the three equal sides is twenty centimeters (20cm).

This is a high skill and very enjoyable activity so organize a work space, gather your tools and materials, (bar compass, moderately sharp pencil, ruler and a large piece of boxboard).        

Remember, you will need a bar compass that can span a minimum of 20cm.
1. Cut out a piece of boxboard approximately 25cm X 25cm.

2. Draw a base line exactly 20cm long. Set your compass radius at 20cm.

3. Place the point of the compass at the beginning of the line and draw an arc of a circle across the top.

4.Repeat drawing the arc with the point of the compass on the other end of the line. The two arcs should intersect. Intersecting means crossing each others path.

5. Where the arcs intersect, join that point to the beginning and end of the line. This will form an equilateral triangle.
When you have completed designing constructing and cutting your four equilateral triangles to your satisfaction, you are ready to layout and assemble your tetrahedron.
20 cm long line
Arc of a circle