Trig stations, short for Trigonometrical station, is a fixed survey point that indicates that you are at the highest peak of a mountain or hill. These days in Australia they tend to look the same consisting of a simple metal structure as shown below.
Prior to the more modern metal Trig stations being erected they typically were rock pillars that took on various forms. The example immediately below is over 120 years old.
Atkinsons Trig on the Burbong Heritage Trail. This Trig Station was erected in the 1880’s
Mount Franklin Trig station. This is the typical Australian trig station that is erected on most mountain summits these days
Mount Stilwell Trig in Kosciuszko National Park