How did the federal government attempt to hinder the efforts of abolitionists in the united states?

One of the actions done by the federal government to hinder the efforts of abolitionists in the United States is that "They put a gag rule into effect which prevented members of Congress from discussing any petition that promoted antislavery." A gag rule is defined as the prohibiting of the discussion on certain topics in the legislative. 

What was the length to begin with?