If you're working with a metal fitting that needs to be tight, you'll want to avoid scratching it during the process. The best way to do this is to use a cloth or other material as a buffer between the wrench and the metal. This will help prevent any direct contact that could scratch the surface. You can also use a lubricant on the fitting before tightening it. This will help reduce friction and make it easier to turn without risking damage to the surface.