A rule of thumb for setting up a ladder safely by positioning the legs of the ladder one foot away from the base of the wall for every four feet of height.

A tool used in prehospital and emergency medicine to estimate the total body surface area affected by a burn, assigning percentages (mostly 9%) to various major body parts.

(US) An airline's policy of putting a passenger on the next available flight without a penalty if they arrive too late for the scheduled flight.

plural of flat tire rule

A rule that prevents a potential competitor from entering the Olympic Games unless they take part in an international event and are placed in the top 30% or the top 50 competitors, whichever is fewer.

Alternative form of three-second rule

plural of three seconds rule

(law) A feature of the copyright law of some countries, whereby the duration of protection granted by the country in question to a work created in a foreign country is limited to no greater than that which it would have received in its country of origin, even if it would have been eligible for a greater duration had it been created in the country in question; the rule that, when a copyrighted work passes into the public domain in its country of origin, it will also pass into the public domain in the country in question if it has not already done so.

(film) The filmmaking principle that the perspective of the camera should remain on one side of an imaginary line so that subjects maintain their spatial relationship.

Alternative form of Vegas rule