PURPOSE: To freely change the width, height and shape by combining plural hollow rectangular parallelopipeds equipped with a rigidity not to be deformed and collapsed in a vertical direction and in a horizontal direction.

CONSTITUTION: A fixture 34 of a rigid body linking means is composed of a casing 36, a bolt 38 and respective holes 36' and 38' to be bored for fitting them to side plates 24 or upper and lower plates 22 of a rectangular parallelopiped module M, and further, to the upper and lower plates 22 of a basic module MO, a hole 51' for tight-fitting a pin 51 to compose a combinedly- piling means is provided. By causing the side edge surfaces 24 of plural rectangular parallelopiped modules M equipped with the prescribed rigidity to collide in the horizontal direction and linking them by means of the rigid body linking means, a top board structure 20 can be formed. Further, a wing structure 50 is formed of one rectangular parallelopiped M or plural rectangular parallelopiped modules M to be mutually piled up, the top board structure 20 is combinedly-piled on the upper part of the wing structure M by the combinedly-piling means, and thereby, the shape can be changed as well as the height and width.