A little difficult to describe but you sharpern it by making the edge square to the face of the scaper this corner should be nice and sharp. You then use a tool to roll edge over making a hook. I have used a screwdriver shaft but they are only marginaly hard enough. Put the scraper in a padded vice (no vice marks) and take the tool you have selected to make the hook and pressing down at about 5 degrees and using lots of pressure slide the tool back and forth (drop of oil could help) a coulple of times then increace the angle to about 10 degrees. If you get it right you should be able to feel the hook it should feel like the burr you get when sharpening a knife or somthing. You can put a hook on both coners of the scarper giving twice the time till resharpening. It takes a little practice to get it right so don't give up it realy works good, but if you cut into the glass it will get dull real fast. Gary