Abstract: A combination of block units comprising: a generally H-shaped block unit having a configuration including two symmetrical grooves extending in Y-axis direction in a basic rectangular parallel-piped having X-, Y- and Z-axes intersecting with the right angle with each other, each of the grooves has a base wall which is parallel with X-axis and oppositely inclining side walls intersecting with the base wall with an acute angle, the distance between the centerlines extending in the Y-axis direction on the side walls being half of the length of the parallel-piped in the X-axis direction, a generally T-shaped block unit having a configuration attained by bisecting the H-shaped block unit along the X- and Z-axes thereof, a generally U-shaped block unit having a configuration attained by bisecting the H-shaped block unit along the X- and Y-axes thereof, and a generally T-shaped block unit having a configuration complementary to the U-shaped block unit.