Sporting signs that say their “lock out” at the Philadelphia Convention Center is unfair, members of the Teamsters Local 107 and Carpenters Union Local 8 protested Monday at the Pennsylvania Convention Center in Philadelphia.

The union members have been barred from the center because their unions missed the May 5 deadline to sign onto a new customer satisfaction agreement outlining new work rules. Though Local 107 and Local 8 belatedly agreed to the new rules on May 9, it was too late. Their work now goes to members of the four unions that signed the new rules in time.

According to Bob McClintock, senior vice president and chief operating officer for SMG, which manages the center, the protesters didn’t interfere with the 11th Annual World Congress on Industrial Biotechnology, which started Monday. "It was a relatively small protest at the back of the building, and it didn't interfere with the move-in at all." The congress is expected to bring 1,100 attendees to the convention center over its four-day span. Security and police were out in force on Monday, according to philly.com, but the protests were civil. The protesters did not return on Tuesday, McClintock says, and all is proceeding normally at the center.

"The key here is the authorities heard the concerns of those who meet in Philadelphia and took affirmative steps to address them, and four of the main unions in Philadelphia did the same thing and renewed their commitment to give people a great place to produce a show," says McClintock.

Note: This article has been updated since its original publication.

More on the protests Monday at philly.com: Union Workers Protest “Lock-out” at Convention Center 

Background on the union situation at the center: Responding to Carpenters Union Strike, Pennsylvania Convention Center Authority Renews Demands