(Present model and then unfold, to show that all sides and the large triangle of which they are composed are equilateral triangles.) On the left edge of the square and 1' from the front left corner, place a point; place a point opposite on the right edge. Join with the ruler these points, and beginning 1" from the left point, draw a line 6" long in the square. Construct on the hoard on a given line, by means of arcs, an equilateral triangle. (Have the pupils see the construction of the triangles in the folding and then draw their diagrams). Bisect all edges of the large triangle, join all adjacent points, fold and sew, leaving one side with loop for hanging.