Spread a chain across the mantle and strike it repeatedly with a hammer, moving the chain in a random manner. This will create indentations that distress the wood mantle.
Casually gouge the fireplace mantle with screwdrivers to create different markings in the wood.
Lay screws on the mantle and strike them with a hammer, leaving thread marks in the wood.
Scuff the mantle randomly with medium-grit sandpaper to rough the surface and make it appear worn.
Wipe the mantle down with a tack cloth, removing any dust created when sanding.
Apply a coat of crackle paint in the color of your choosing using a paintbrush to finish distressing your wood mantle.