A wedding arbor or arch is a curved structure composed of wood, metal or vinyl often used in outdoor weddings. Couples exchange vows and take pictures beneath the arch instead of at an altar. Because the arch plays such an integral role in the marriage ceremony, decorating the arch should be a priority. Using a sheer fabric such as tulle can give the centerpiece a simple yet beautiful look.

Measure the height and width of the wedding arch in yards with a tape measure. Add these numbers together to get an approximate length measurement for the arch. Double or even triple this number to determine how many yards of tulle you will need to decorate the arch.

Purchase the tulle from a local craft or fabric store. Choose a color of tulle to match the bridesmaids' dresses and flowers or stick with a simple white fabric. Some stores even sell tulle with glitter interwoven in the fabric that sparkles, giving it a more romantic look.

Hold the end of the length of tulle and twist the fabric as you wind it around the wedding arch. Wrap the tulle loosely in between the segments of the arch as you make your way from one side to the other.

Secure the ends of the tulle with floral wire on each side of the wedding arch. Tie down any loose ends where you switched colors or ran out of tulle and had to start a new piece. You might have to secure the tulle in the center of the arch as well, depending on how tightly you wound the fabric.

Make bows with the leftover tulle by folding it into six large loops and twisting the loops together in the center with floral wire. Attach the tulle bows to the center of the arch or space them out throughout the wedding arch.