Wainscoting, that wooden paneling used typically on the lower half of walls, adds a bit of a rustic, country or casual vibe to a room. If the wainscoting is new or freshly painted, however, it may look a bit too pristine for the room's decor. Distressing the wood gives it the look of added years and a little abuse that might be typical over time from chair backs and various objects bumping against the walls. It's a means of causing wear quickly rather than waiting decades for it to happen naturally.
Remove dust and cobwebs from the wainscoting using a duster.
Whack the wainscoting in several areas that would naturally receive wear over time, such as at the height of a chair back or the trim at the top of the wainscoting, using a claw hammer. Hit the paneling with various parts of the hammer, such as the claw or side of the hammer, to vary the look. If the wainscoting covers a corner, hit the corner several times with the hammer as well.
Remove small chunks of wainscoting, such as on raised borders, using a chisel and rubber mallet. Use this technique in an area that would receive wear naturally, such as where a doorknob may hit the wall, or at the entry to a stairwell. (Skip this step if you don't want the paneling to look quite so distressed.)
Sand away the paint or finish on parts of the wainscoting using a fine-grit sanding block, focusing on sharp edges, trim, and areas that would receive the most wear over time. Remove dust with a tack cloth.
Drill clusters of several tiny holes using a 1/16-inch drill bit in random areas of the wainscoting to emulate the look of worm damage.