8/15/19 AIM  FIG 2 − 3 − 28 Holding Position Sign for ILS Critical Area FIG 2 − 3 − 29 Sign Prohibiting Aircraft Entry into an Area 3. ILS Critical Area Holding Position Sign. At some airports, when the instrument landing system is being used, it is necessary to hold an aircraft on a taxiway at a location other than the holding position described in Paragraph 2 − 3 − 5, Holding Position Markings. In these situations, the holding position sign for these operations will have the inscription “ILS” and be located adjacent to the holding position marking on the taxiway described in paragraph 2 − 3 − 5. An example of this sign is shown in FIG 2 − 3 28. 4. No Entry Sign. This sign, shown in FIG 2 − 3 − 29, prohibits an aircraft from entering an area. Typically, this sign would be located on a taxiway intended to be used in only one direction or at the intersection of vehicle roadways with runways, taxiways, or aprons where the roadway may be mistaken as a taxiway or other aircraft movement surface. Holding position signs provide the pilot with a visual cue as to the location of the holding position marking. AIM Paragraph 2 − 3 − 5, Holding Position Markings NOTE − REFERENCE − Airport Marking Aids and Signs 2 − 3 − 22