Abstract: A drill jig for producing a rectangular mortise in the flat surface of a workpiece requiring only a portable drill and drill bit. The rectangular slot is intended to snugly house a standard square or hex nut so as to keep it from turning in either direction. The jig also permits production of a pilot hole perpendicular to the mortised slot for receiving the threaded end of a bolt for mating with the embedded nut. The drill jig in a preferred embodiment includes a pair of substantially identical drill guide members, an anvil plate, and a stationary support, all of which are movably disposed on a vertical support member. The workpiece is clamped between the lower drill guide plate and the anvil plate. Each of the drill guide plates includes a channel-shaped member having the desired slot templates formed therein, and a movable template disposed therewithin.