Abstract: A lightweight portable jig assembly for supporting a power drill and for advancing and retracting the drill towards and away from an overhead workpiece comprises a carriage having a first tubular portion slidable on a tube standard and a second tubular portion within which slides a second tube on which the drill is mounted. A releasable lock mechanism is cooperative relation with the carriage and tube standard prevents downward movement of the carriage on the standard while permitting upward movement of the carriage on the standard whereby the carriage may be selectively positioned on the standard simply by lifting the carriage to the proper vertical height and then released to lock same in place. Advancement and retraction of the drill towards the overhead workpiece is obtained by a manually operable lever and linkage which further is operable to effect automatic release of the releasable lock mechanism upon retraction of the drill.