These four triangles are bound together even though no two triangles are linked. If one triangle were removed, the rest would fall apart.
About five feet of 5/16 inch dowel. You can use another size of dowel as long as you adjust the length.
Cut 12 pieces of dowel so that each end comes to a point that is 30° and that the longest dimension of the dowel is 4.5 inches long (11 cm). I recommend creating a jig to hold the dowels at the appropriate angle since most miter saws can't cut at such a steep angle. I made a jig out of a scrap of plywood that I cut in the shape of an equilateral triangle. The dowel was fastened parallel to one side of the triangle. The jig could then be placed on a compound miter saw holding the one side of the triangle against the guide, making a cut and then swinging the jig so the other side was against the guide and cutting again.
Glue three triangles together and glue two sides of the fourth.
Assemble the triangles and slip the last side in place and glue it.
Alan Holden's book has a wealth of interesting models to make out of wooden dowels. The book has fascinating and intricate models. However, unless you are a serious model-maker, most will be too difficult to create.