The authors identify two types of simple rules: Those that can help you make decisions and those that can help you do things.
Decision rules set boundaries, prioritize alternatives, and establish stopping points. The disastrous ascent of Mount Everest that resulted in eight deaths in 1996, chronicled in Jon Krakauer’s best-selling book Into Thin Air, was precipitated by the violation of a single rule that had been set by Scott Fischer, an expedition leader: “If you aren’t on the top by 2:00, it’s time to turn around.” (Any later and the risks were exponentially greater because the exhausted climbers would have to make the descent to their camp in the dark.) After unexpected delays, Fischer and most of the party ignored the rule and kept climbing. Fischer himself didn’t summit until 3:45 p.m. Unfortunately, his body is still on the mountain.
(From Theodore Kinni on Quartz)