chain gang 
noun
A group of convicts chained together while working outside the prison.Following his arrest, he is tried, convicted, and sentenced to one year on a prison chain gang in a distant parish....
- The next scene, playing under the credits, is of the typical, grueling road work forced upon prisoners - an imprisonment which reflects the authentic horrors of life on a chain gang in a Southern prison.
- Directed by the Coen Brothers, the film is set in depression-era Mississippi and follows the trails of three convicts who escape a chain gang and go in search of buried treasure.