The breaking of the glass. At the conclusion of the ceremony, the groom smashes a glass with his foot. One interpretation is that the marriage will last as long as the glass is broken-- forever. Another interpretation is that people need to remember those who are suffering even in their greatest moments of joy, and to remember the destruction of the second temple. After the breaking of the glass, the guests yell, "Mazel Tov!" which means good luck or congratulations!