Tying the Knot
The expression "tying the knot" actually dates back to Roman Times when the bride wore a girdle secured by a knot. On the wedding night, the groom then had the honors of "untying the knot." The couple's lives were then tied together. Rituals of binding were also popular in ancient Carthage. The couple's thumbs were laced together with a strip of leather. In India, the Hindu groom knotted a ribbon around his bride's neck, and once tied, the marriage was legal and binding. For much of history the rope was the most powerful way to connect things and people. So, it made sense to talk about "tying the knot."
 

Jumping The Broom
The most widely known African American wedding tradition is "jumping the broom".  According to Thony Anyiams, a Nigerian wedding fashion designer, the tradition is an African one, used by enslaved Africans in America as a way to maintain their ties to their culture and their homeland. They jumped the broom because that is the way weddings were  ritualized in their African homeland.

What is jumping the broom? Simply, it is a ceremony in which the bride and groom, either at the ceremony or reception, signify their entrance into a new life and their creation of a new family by symbolically “sweeping away” their former single lives, former problems and concerns, and stepping over the broom to enter upon a new adventure as husband and wife.
 

Sawhorsing
Sawhorsing is an Italian tradition. The people in the village would set up a sawhorse, a log and a double handle saw. The newlyweds must saw the log apart with the prompting and cheering of the crowd. When the job is finished and the log cut, it symbolized that the man and woman must work together in all of life's tasks.