Swing Door trains, commonly known as "Dogboxes" or "Doggies", were wooden-bodied electric multiple unit (EMU) trains that operated on the suburban railway network of Melbourne, Victoria, Australia. Swing Door cars had outward-opening doors. They were reasonably narrow, to ensure that two passing trains could not foul each other if doors were accidentally left open. At certain locations clearances were tight and there are stories of Swing Door cars losing doors that were not closed. The fleet could be seen running in any arrangement, from one car (using a double-ended M car), up to seven cars.