A flatiron, or flattie, is a type of coastal trading vessel designed to pass under bridges that have limited clearance.
Most were colliers built to bring coal from North East England and South Wales to gasworks and power stations on the River Thames that were upriver from the Pool of London.
[2] By the middle of the 1940s flatiron motor ships with marine diesel engines were being built.
[3] The Gas Light and Coke Company's collier fleet included flatirons to serve its gasworks at Fulham and Nine Elms.
By the mid-1980s the need to carry thousands of tons of coal on the Thames above the Pool of London had ceased.