The CRL Thick Glass Cut Opening Tapper operates on a spring driven bolt principle. This unique glass working tool opens and runs score lines in glass from 3/8" to 3/4" (10 to 19 mm) thick. It features an industrial steel body that has a chemically applied nickel coating. This finish helps to preserve and protect it from the day to day abuse a tool of this type can be subjected to. The internal spring mechanism adjusts to regulate the tapping force from very light for thinner glass to a powerful punch for thick plate glass up to 3/4" (19 mm). No more need for using a tapping ball or small ball pein hammer; both of which can be inaccurate and can break or mar your glass. From the first time you try this heavy-duty tool, you can tell it's a high quality product.