fool·proof 
/ˈfu:lˌpru:f/ adjective
/ˈfu:lˌpru:f/ adjective [more foolproof; most foolproof] : done, made, or planned so well that nothing can go wrong
▪ foolproof directions ▪ a foolproof plan ▪ DNA fingerprinting gives police a virtually foolproof way to link a suspect to a crime scene.
▪ foolproof directions ▪ a foolproof plan ▪ DNA fingerprinting gives police a virtually foolproof way to link a suspect to a crime scene.
