Its like a portable drill press for precision alignment, V-groove along the bottom of the guide allows for perpendicular alignment with all drill sizes on round parts and corners, Image shows top and bottom of guide, Bottom surface is precision ground to assure stability and accurate perpendicular alignment on flat surfaces, Special nickel alloyed steel heat treated for durability, Non-plated material with light oil coating to prevent rust, Alignment marks on guide to line up on center, Drill Straight - Every Time, 17 drill sizes: 0, 125 to 0, 375, Dimensions: 7, 75L x 1, 125H x 5, 125W, SKU: BGTRL001