Why are pillars placed on the pedestals of the WM, SW and JW?

The pillars placed at the stations of the principal officers represent the three grand pillars said to support a lodge: Wisdom, Strength, and Beauty 23. The Master in the East represents the column of Wisdom, the Senior Warden in the West represents Strength, and the Junior Warden in the South represents Beauty 2.

In practical lodge work, the miniature columns on the Wardens' pedestals also serve as visible indicators of the lodge's status 1. While the lodge is at labor, the Senior Warden's column stands erect while the Junior Warden's lies prostrate 1. When the lodge is called to refreshment, the positions are reversed: the Junior Warden erects his column and the Senior Warden lays his down, allowing brethren to tell at a glance whether the lodge is at work or rest 1.