In a hospital, a stretcher is a device used to carry a person who must lie flat and can't move on their own. It takes two strong people to carry a patient on a stretcher.
Although the words are sometimes used interchangeably, a stretcher is different from a gurney, which is fitted with wheels and can be moved by a single person. Stretchers are more portable and tend to be used in emergency situations, especially on battlefields and in wilderness search-and-rescue operations. When an artist, (rather than a doctor or ambulance driver) uses the word stretcher, they generally mean "wooden frame on which a canvas is stretched for painting."