A cummerbund is a wait sash that is worn with single-breasted tuxedos. The cummerbund is typically made of satin or silk and is considered a throwback to popular fashion of the 1970s. The general rule is that with a formal tuxedo, either a vest or cummerbund should be worn, but never both. The most popular use for cummerbunds is for men in weddings, usually the best men. Putting on and wearing a cummerbund is a fairly simple process that can be executed in few quick steps.
Lay out your cummerbund on a flat surface and stretch it out. Don't iron the cummerbund, but make sure to stretch some of the larger frills caused by the pleated material.
Put on you suit and begin to put on the cummerbund before you put on your tie. Make sure your dress shirt is tucked into your trousers before putting on the cummerbund.
Wrap the cummerbund around your waist, making sure the pleats are facing up. The pleats, or flaps, face up because the original use of a cummerbund was to catch crumbs, but it is now used as an aesthetic item to complement the transition between the shirt and waistband of the trousers.
Fasten the ribbon around your back or fasten the buckle, similar to a belt. Some cummerbunds also have a Velcro attachment, but the ribbon tie is usually the most preferred. After it is fastened, put on your tie or bow tie and make sure it matches with the cummerbund. If you're wearing a military cummerbund, continue to Step 5.
Wear a leather belt above the military cummerbund, which should be specific to the military ceremony for which it's worn. The other difference from a typical formal cummerbund in that one end of the cummerbund should be hanging with an ornamental fringe (see References).