A kit for building a structural shape can include at least one planar panel having at least three sides, including a first side and having a first end and a second end, a second side connected to the first end and extending from the first side at a first angle, and a third side connected to the first end and extending from the first side at a second angle. A first connector can be formed with the first side and define a first slot having a first blind end substantially located at the midpoint of the first side. A second connector can be formed with the second side and define a second slot having a second blind end. A third connector can be formed with the third side and define a third slot having a third blind end.