There are two types of Runway Taxi-Holding Positions (RTHP): Runway Holding Positions and ILS Critical Area Holding Positions. If only one type is present, it will always be the former. Where there is more than one RTHP, all the additional ones will be of the second type.
ILS critical area holding positions look like a “ladder” mark laid across the full width of the taxiway and normally at right angles to its centerline.
Air Traffic Control protects the ILS Critical Areas when arriving aircraft are inside the outer marker/final approach fix (FAF) on an ILS approach, and the reported ceiling is less than 800 feet or visibility is less than 2 miles. Basically, if the weather is bad and arrivals can’t see the runway well, they must use the ILS. Past the ILS critical area, aircraft and vehicles on the ground will interfere with the signal, making it very hard for the arrival to find the runway with the localizer and glideslope.