Abstract: Three traveling blocks confined to rectilinear paths are propelled to and fro in those paths in coordinated programs of motion by program-controlled motors. A leg member for each of said blocks is flexibly connected at one of its ends to its respective traveling block. The three legs are flexibly interconnected at locations on the legs away from the blocks. The three legs combine the programmed rectilinear movements of the blocks to produce a corresponding programmed three-dimensional movement of a tool carried by one of said legs.