Truncated Octahedron with Square Faces Concave (CFW 255)

Instructions for this model can be found in Shuzo Fujimoto’s books:

• Solid Origami, page 43 (CP)
• Invitation to Creative Playing with Origami, pages 57 (picture of folded model), 63 (CP), and 123 (example of space-filling by folded models)