I too have a scar on the heel of my hand. I used to be a catering manager for Marriott and was running a deli buffet lunch for a couple hundred people. We ran out of sliced hard rolls, so I ran to the kitchen and started slicing with a nice big serrated knife. Straight through to the bone, 8 stitches to close. After that, I highjacked one of those kevlar-steel meat cutting gloves from the chefs and always wore it on my left hand when slicing rolls and bagels.