A safety management tool used to explain how different but connected systems are related in achieving process safety. The barriers that prevent, detect, control, and mitigate accidents are depicted as slices of the cheese with each having a number of holes of differing sizes. The size and number of holes in each slice represents the imperfections in the barrier and are defined as specific performance standards. Well-managed processes have few or small holes. When two or more slices are put together, protection can be achieved and represented as the coverage of holes. (p. 369)