An apparatus for three-dimensional (3D) printing of an object comprises a print head having at least one inlet for receiving material to be extruded and an outlet. The print head is configured, when the outlet is completely unblocked, to extrude a sheet of material of the width and height of the outlet. One or more actuators are positioned along the width of the print head and arranged to controllably block one or more sections along the width to prevent material from being extruded through the blocked sections, enabling selective extrusion of material through sections that are not blocked in order to selectively print a width of an entire layer of the object in a single pass. The print head and the object move relative to one another via one motion of the print head or of the object.