In the Radius menu, turn on 4 inch circles, by clicking on the number 4. Add 10 degrees to the Azimuth menu by typing the number "10" in the blank next to "AzimuthValue:" and clicking "Add!" on the Azimuth line. Select "0" in the Slope menu (it is probably already selected). Click "New!" on the Line menu. This will add the entry (10 0) meaning azimuth 10 degrees, slope 0 degrees to the line menu and activate it. We will use these alignment lines to construct the first line of a tetrahedron. This direction of line is chosen because it orients the tetrahedron nicely for viewing from the default camera position.

Start with an empty viewer. Add a roughly horizontal line segment in the center of the screen (Shift Left-Mouse places the first endpoint; Shift Middle-Mouse places the second). Make the leftmost vertex hot (select it with Left-Mouse; make it hot with Ctrl-S). An alignment line and alignment sphere will appear as shown in Figure 1(a). Select the cold end of the line segment and drag it (Ctrl Left-Mouse and hold down). Snap the software cursor, the skitter, to things. Notices that the z axis of the skitter stays perpendicular to the surface of the sphere when you snap to it as shown in Figure 1(a). Snap the skitter to the intersection point of the sphere with the alignment line as shown in Figure 1(b).

For extra credit: Turn on alignment lines of azimuth-slope (90 0). Snap the skitter to the two intersection points of this line with the sphere. A bit harder, yes? Gargoyle3D doesn't draw intersection points, yet. Perhaps someday it will.

Make the other end of the line segment hot. Now you have two alignment spheres. Also, the circle of intersection of the alignment spheres is drawn. If you look closely, you'll see that the circles representing alignment spheres are drawn gray, while the ellipse representing the circle of intersection of the two spheres is black. Add a line segment from one end of the line segment to the far side of the circle of intersection to get a picture as in Figure 2(a). Add a line segment connecting the two lonely line segment ends to complete an equilateral triangle in 3D.

Make the third vertex hot. Now you have three alignment spheres and three intersection circles. Add a line segment from any vertex of the triangle to the upper point where all three intersection circles meet. The feedback line will tell you that you are on "a (align sphere/align sphere circle)/(align sphere) intersection point" and your picture should look like Figure 2(b). Make everything cold (Ctrl-Shift Double-S). Add line segments from the new vertex to the last two vertices of the equilateral triangle. You should have a picture like Figure 2(c).

For extra credit: use segment select (Middle-Mouse) to select one segment of the tetrahedron. Use extend select (Right-Mouse) to extend the selection to the other five segments. Place the skitter on the lower left vertex (Shift Left-Mouse). Copy and drag the tetrahedron (Ctrl Double-Left-Mouse), snapping the copy to the lower right, backmost and topmost vertices of the original tetrahedron to produce Figure 3.