Masonic Mark

what does the equilateral triangle symbolise in the mark degree and where does that reading come from

The claim that an equilateral triangle served as a mark of approval in operative masonry is apocryphal, carrying no historical sanction or foundation in the practice of the operative craft. Mackey observes that no masonic marks have been identified on ancient Jewish buildings or King Solomon's Temple, treating narratives that ascribe this function to the triangle as unhistorical inventions rather than genuine operative carryovers.

Mackey