THE RESULT: Mangled edges.THE FIX: That gooey, sticky quality that endears brownies to us is also the reason they often end up in sloppy squares when they’re cut. The culprit is likely the metal knife you’re using, particularly if you’re cutting still-warm brownies, which don’t hold together as well as cooled ones. The secret weapon: a plastic knife or thin silicone spatula. Both lack sharp edges for the brownie bits to cling to, so they cut more smoothly through without picking up crumbs, and they work even if you’re cutting brownies that haven’t completely cooled. Plus, plastic and silicone won’t damage pans like metal knives will.