Automatically centers itself on round, square or irregular shapes. Handles stock up to 2-Inch thick. Drill-hole sizes are 1/4-Inch, 5/16-Inch, 3/8-Inch, 7/16-Inch and 1/2-Inch. Six hardened steel bushings are provided: 2 each of 1/4-Inch, 5/16-Inch and 3/8-Inch. You can drill two identical parallel holes without moving the jig. Easy to use.