Carpenters union sings sad song

Members of the Metropolitan Regional Council of Carpenters hold a protest rally outside the Pennsylvania Convention Center protest at the entrance at N. Broad St. at Arch on Friday morning July 11, 2014.. The union's fat cat doll symbolizes "the man" holding them down, locking them out and refusing them work. (Alejandro A. Alvarez / Staff Photographer)

With their loudspeakers playing the jaunty 1961 Marvelettes Motown hit, "Please Mr. Postman," union carpenters and Teamsters picketed outside the Pennsylvania Convention Center during a gathering of the National Association of Letter Carriers Union.

Leaders of the two unions say they were unfairly ousted from the center because they didn't sign a new Customer Satisfaction Agreement on time, but did sign a few days later.

Convention center management said the leaders were well aware of the deadline and chose not to sign. The two unions' work was then divided among the four other unions working at the center.

The letter carriers convention, which began Sunday and runs through Saturday, is expected to draw 12,000 letter carriers and family members and generate $24.8 million in economic impact.