Features: 5 standard drill bit sizes, namely 1/4", 3/8", 5/16", 7/16" and 1/2"; allow you to easily apply it to mortise and joints, build furniture and repair tables, making for planking. There are 4 holes on the top of the clamp, 2 of which can be installed with threaded bushings, which can be replaced with 1/4", 3/8" and 5/16", and the other 2 holes can be installed with 7/16" and 1/2" drill bits, making tool for various woodworking projects. Make closet shelves that require flat panel connection, make some shelves, cabinets, desks, breakfast tables, shutters in the garage, repair doors that were accidentally damaged by children, make floating shelves, install railings. The engraved lines seen on the front are used for direct center alignment. Alignment can be done visually, and when the middle bolts is turned, the aluminum clamps on both sides will be tightened at the same time, and the plate will be clamped evenly so that the position to be perforated is in the exact center. The aluminum surfaceS is anodized and is not easy to leave scratches. The screws are chrome-plated to prevent rust and are more stable. Specifications: Component:Aluminum Type:inch/Metric Size:Approx.12x6.5cm/4.72x2.56inch Package Includes: 1Pc Dowel Jig 6cs Drilling Bushing note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.