Airport Markings  Action or Purpose Type of Marking  Holding Position:  Denotes entrance to a runway from a  taxiway, approach hold position on a  taxiway, or LAHSO holding position  on a runway.  ILS Critical Area Boundary:  Denotes entrance to an area to be  protected for an ILS signal.  Taxiway/Taxiway Holding Position:  Denotes location on taxiway or apron  where aircraft hold short of another  taxiway.  Non-Movement Area Boundary:  Delineates movement area under  control of ATC, from non-movement  area.  Surface Painted Holding Position:  Denotes entrance to a runway from a  taxiway.  Enhanced Taxiway Centerline:  Provides visual cue to help identify  location of a runway holding position  on a taxiway. These markings are  installed 150 feet prior to the holding  position markings.  Surface Painted Taxiway Direction:  Defines designation/direction of  intersecting taxiway(s).  Surface Painted Taxiway Location:  Identifies taxiway on which the  aircraft is located.  Taxiway Edge: Solid Double Yellow Lines  Defines edge of usable, full strength taxiway. Adjoining  pavement  IS NOT  intended for use by aircraft.  4-22  4-22  T  B  Taxi direction  T axi direction  Type of Marking  NON-USEABLE Action or Purpose  Type of Marking  Taxiway Edge: Dashed Double Yellow Lines  Defines taxiway edge where adjoining pavement  IS USABLE , such as along an apron or ramp.  Action or Purpose  USEABLE USEABLE  Figure C-3.  Samples and explanations of standard airport markings.  C-4 