A mechanism which structurally, physically, or electronically blocks human beings from committing an error.
Walls, locks, and barbed-wire are examples of a structural error-impossibilitator. And the way Web pages are programmed to not allow a user to proceed to the next step until the user types their password, for example, is an example of an electronic error-impossibilitator. Condoms and other pregnancy-prevention devices are also error-impossibilitators. However, some error-impossibilitators are not fool-proof. Parents, teachers, mentors, coaches, personal trainers, security guards or bouncers are not error-impossibilitators because—unless they stand in someone's way—they can only help others prevent errors. Error-impossibilitators are of two types, those that can be circumvented, such as by cutting a barbed wire, and those which cannot be circumvented, such as the wall President Trump offered to build on the U.S.-Mexico border. Note that very few error-impossibilitators are 100% reliable because if someone wants to, they can, for example, dig a tunnel under a wall, as people have done to get to the other side.