Drilling jigs consisting of a first substantially rectilinear bar (2) having a plurality of through holes (4) through which holes can be drilled in a surface, and a plurality of locator members (6, 7, 8) which are rotatable relative to one or other of the surfaces of the bar (2) other than those through which holes are to be drilled, the jigs further including a second substantially rectilinear bar (17) with a plurality of through holes (17) through which holes can be drilled in a surface, and securing means (12, 13) for securing the first and second bars to each other, the holes in the first and second bars through which holes are drilled being substantially in alignment when they are secured together with the securing means.