Building block having flexible ribs to engage a similar block

Claim 1

A BUILDING BLOCK COMPRISING A FLAT SURFACE, A PLURALITY OF WALLS EXTENDING FROM SAID FLAT SURFACE AND CONNECTED TOGETHER TO PROVIDE A BOX-LIKE MEMBER HAVING A HOLLOW SPACE WITH AN OPENING, A PLURALITY OF DISTINCT FLEXIBLE INDEPENDENT RIBS ON SAID FLAT SURFACE PROJECTING IN A DIRECTION AWAY FROM SAID WALLS, SAID RIBS EXTENDING ALONG A BOUNDARY PATH WHICH IS COMPLEMENTARY TO THE OUTLINE OF THE WALLS DEFINING THE OPENING OF THE HOLLOW SPACE SUCH THAT TWO BUILDING BLOCKS CAN BE CONNECTED TOGETHER IN SELF-ENGAGED LOCKED FASHION BY INSERTING THE RIBS OF ONE BLOCK INTO THE HOLLOW SPACE OF THE OTHER OF THE BLOCKS TO CAUSE THE RIBS TO BE RESILIENTLY DEFORMED AND HOLD THE BLOCKS TOGETHER, SAID RIBS INCLUDING UNDERCUT OUTWARD FACING SURFACES, THE INSIDE SURFACES OF THE WALLS OF SAID BLOCK INCLUDING UNDERCUT INWARD FACING SURFACES WHICH INTERENGAGE WITH THE UNDERCUT SURFACES OF THE RIBS OF ANOTHER BLOCK AFTER INSERTION THEREOF AND AFTER HAVING ELASTICALLY DEFORMED THE SAME.