Abstract: This invention relates to a roof bolt injection mast comprising an elongate member having a length slightly less than the height from the floor to the roof of a tunnel or gallery in which the mast is to be operated, the elongate member being provided with a passage which extends therethrough from one end to the other and a port extending through the sidewall thereof to communicate with the said passage, a portion of the passage extending from the lower end of the member to the point of communication with the port being enlarged whereby a fluid introduced through said port will provide the means whereby a first piston disposed in the enlarged portion of the passage is operable to lock the mast between the floor and the ceiling while a second piston disposed in the main passage provides the means whereby a roof bolt disposed therein will be injected into the roof under the influence of the fluid introduced through the port.