By popular demand, I am posting instructions for how to make
your own Impenetraball, one of my most popular sculptures. Be
warned; this is not easy, but it is certainly rewarding. And
potentially lethal, in more ways than one…  Final Impenetraball
Geometry of the Impenetraball  Impenetraball schematic  First,
we must understand the geometry of the Impenetraball. Despite
its spherical appearance, the pattern is based on a cube. As
illustrated in the schematic above (each square cell represents
one binder clip), there are six 4×4 grids of clips that
correspond to the faces of a cube (shown in blue), and these
faces are joined with additional clips (green) along the cube’s
12 edges. Note that the faces are not joined head-on; instead,
they are offset by 1 clip from their neighbors, and this “twist”
leaves a triangular hole at each of the cube’s 8 vertices
vertices. The face and corner features are shown below.
Impenetraball face and corner  The main Impenetraball page goes
into a bit more depth about the piece