1. Draw a circle. 


2. Place your compass point on the edge of the first circle and draw another circle. 
3. Place your compass point on an intersection and draw a third circle. 


4. Draw line segments connecting all the intersections. (Use your straight edge. You can score the lines with a ballpoint pen.) 
5. The four triangles will become the four faces of the tetrahedron. Mark three tabs with a T, as shown. (You'll use the tabs to glue the edges of the triangles together.) You will not need the shaded sections. Carefully cut out around the white areathe four triangles and three tabs. 


Note: You may notice that you've used a whole sheet of paper to create a fairly small space form. If you want to make the largest possible tetrahedron out of one sheet of paper, you do not really need to draw three full circles on the paper. Open your compass wider and place it as shown so that your triangles and tabs still fit on the paper but unneeded portions of the circles get cut off. 
6. After you have cut out your shape, fold carefully along each line. (If you draw your lines firmly with a ballpoint pen, that "scores" the paper so it is easier to fold. Also, it helps to lay your straight edge along the line as you are folding.) Fold the tabs down, too. Check to be sure that the point of one folded triangle meets up with the point of the triangle underneath it. Crease each fold with a fingernail or the side of a pen or pencil so that each fold is very crisp. 


If you are going to decorate your space form, it is easier to do this before you glue it. (Be sure to decorate the blank side, not the messy side with all of the curves and lines.) 