Building block

A substantially rectangular-shaped building block comprising

• a. a substantially flat front face,
• b. a substantially flat rear face, spaced from said front face in substantially parallel relation thereto,
• c. two oppositely disposed sides extending the length of said block between said faces, and
• d. two oppositely disposed ends extending the width of said block between said faces,
• e. each of said sides having
• (1) two oppositely disposed, substantially uniplanar end portions, and
• (2) an intermediate indentation separating said end portions,
• f. each of said end portions and each of said intermediate indentations having a length, parallel to said faces, equal to the width thereof, perpendicular to said faces,
• g. each of said intermediate indentations having a depth, perpendicular to the plane of the adjacent pair of said end portions, equal to one-half of said width thereof,
• h. each of said ends having
• (1) two oppositely disposed, substantially uniplanar end portions, and
• (2) an intermediate indentation separating said last mentioned end portions,
• i. each of said last mentioned end portions having
• (1) a length, parallel to said faces, equal to one-half said lengths and widths of said first mentioned end portions and said first mentioned indentations, and
• (2) a width, perpendicular to said faces, equal to said lengths and widths of said first mentioned end portions and said first mentioned indentations, and
• j. each of said second mentioned indentations having a length, parallel to said faces, a width, perpendicular to said faces, and a depth, perpendicular to the plane of the adjacent pair of said second mentioned end portions, equal to said length, width and depth, respectively, of each of said first mentioned indentations,
• k. said intermediate indentations and said second mentioned indentations being adapted to matingly receive portions of other blocks which have dimensions matching those of the indentations.