To provide a building block type combination block for people of all ages from children to adults to the elderly, combining and piling up right triangular pyramids (regular tetrahedrons) and square pyramids of optional sizes for molding by using a suitable number of only two kinds of solids: right triangular pyramids (regular tetrahedrons) and square pyramids, and besides enabling various molding, although most of the conventional building block type combination blocks are mainly for infants and children as a toy.

The shapes of faces constituting solids of right triangular pyramids (regular tetrahedrons) and square pyramids having the same side length 1 are all equilateral triangles except the base of the square pyramid, and when the solids are combined, the faces of the equilateral triangles are matched to generate continuity, thereby molding various combinations. A suitable number of solids are combined to optionally mold right triangular pyramids (regular tetrahedrons) and square pyramids having an integer multiple of one side length 1 and besides freely mold its similar form and continuous form. Thus, the children to adults and persons of advanced age are allowed to enjoy the process of its creation, and have joy by a sense of achievement to complete a unique molding.