TRESTLEBOARD

In Freemasonry, the trestleboard is a deeply significant symbol, drawing its meaning from the historical practices of operative stonemasons and applying them metaphorically to the lives of "speculative" (modern) Masons.

Here's why Masons have a trestleboard:
In the days of operative stonemasons, a trestleboard was a physical board, often placed on trestles (supports), where the Master Mason or architect would draw the designs, plans, and blueprints for the building project. This board provided the precise instructions, measurements, and layouts that the workmen and apprentices needed to follow to construct the building with accuracy and propriety.