About This High quality aluminum (drill guide) and die steel(bushing),high hardness and strength,good wear-resistant and durable to use,the drill bushings is in imperial (inch) sizes,1/4" 3/8" 5/16" ,not metric. Adjustable width for different thick，For stock from 5/8" to a full 1” thick and more. The parallel arms open to accommodate stock up to 2.4” thick. Attach the jig's adjustable center bar end-stop for drilling two or three precisely spaced end grain holes. This feature allows perfect alignment of face frame stiles and top and bottom rails. The handy inch scale lets you accurately set the stop. The second alignment feature lets you drill a series of equally spaced holes along the edge of a board. Just attach the supplied pin in the center bar, insert the pin in a hole and drill more holes. The arms of self centering dowel jig jig are an always-reliable parallelogram that never fails to find dead center. Simply align the precision-machined notch on the jig's center bar with the dowel location mark on your board, hold the jig and drill.
