Building elements

Building elements of predetermined number with matching side surfaces for fitting all of the predetermined number of building elements together to form construction of varying shape, each said building elements having the same length (L) and each having two opposite, equiform, flat, parallel end surfaces and at least three flat, rectangular side surfaces extending between said end surfaces thereby to present said matching side surfaces, the cross-sectional surfaces of the building elements each having a size which is a multiple of a triangular area of the size a.sup.2 /2, and the sides of the end surfaces having proportional lengths selected from the group consisting of a, a.sqroot..sup.2, 2a and 2a.sqroot.2 or a multiple thereof, "a" having a predetermined value, and the sides of the end surfaces defining proportional angles selected from the group consisting of 45.degree., 90.degree., 135.degree. and 270.degree., said building elements to form said varying shape constructions being non-congruent, having non-congruent matching side surfaces and being always a nine in number said nine building elements being divided into three groups, a first group comprising a right-angled isosceles triangle, the equal sides of which each has a length a, a rectangle with sides a and 2a and a parallelogram with sides a.sqroot.2 and 2a, a second group comprising a right-angled isosceles triangle, the equal sides of which each has a length a.sqroot.2, a parallel trapezium with sides a.sqroot.2, 2a and 2a.sqroot.2, and a symmetrical pentagon defining with respect to its line of symmetry two parallel trapeziums having sides a, a.sqroot.2, the third of said three groups of building elements comprising a right-angled isosceles triangle, the equal sides of which each has a length 2a, a symmetrical pentagon defining with respect to its line of symmetry two parallel trapeziums having sides a.sqroot.2 and 2a, and a symmetrical hexagon defining with respect to its line of symmetry two parallelograms having sides a.sqroot.2 and 2a, the end surfaces of the first group of building elements each having a height a, the end surfaces of the second group of building elements each having a height a.sqroot.2 and the end surfaces of the third group of building elements each having a height 2a, all of said nine non-congruent building elements always being fitted together with predetermined of said side surfaces adjacent each other to form constructions of various shapes of varying cross-section but of the same area, 20a.sup.2.