The Sentinel boiler was a design of vertical boiler, fitted to the numerous steam wagons built by the Sentinel Waggon Works. The boiler was carefully designed for use in a steam wagon: it was compact, easy to handle whilst driving, and its maintenance features recognised the problems of poor feedwater quality and the need for it to be maintained by a small operator, rather than a major locomotive works. Although this design was used in most of Sentinel's products, they also produced larger boilers of quite different types for their railway locomotives.