Explain third degree tracing board

The design exhibited on the third degree tracing board includes the mausoleum of the Master-Builder, setting the symbolic context following his death 2.

Among the symbols depicted, William S. Rockwell identified the emblem of a cubic stone with an axe driven into it as particularly suggestive 1. Rockwell compared this emblem to an Egyptian hieroglyphic associated with Seth—a smooth stone with a knife—which signified falsehood and error, in contrast to the rough stone representing truth and faith 1.

Earlier designs, such as the tracing board of 1776, depicted a ladder or steps reduced to three 1. While Albert C. Mackey noted that this three-stepped delineation was likely a matter of practical convenience—since a Masonic ladder properly contains seven steps for the cardinal and theological virtues—the three steps on the Master's carpet represent the three stages of human life: youth, manhood, and old age 1. Symbolically, these steps mark a passage from darkness and ignorance through death into eternal light and spiritual knowledge 1.