What is the reference used to locate the center point of the wellway called?

The reference used to locate the center point of the wellway is referred to as a column line. This is crucial in the installation of escalators, as it provides a vertical alignment that ensures the escalator system is installed correctly and operates efficiently. The column line serves as a foundational guide that helps in determining the placement of the escalators relative to the surrounding structure, ensuring that the installation meets design specifications and safety standards. Proper alignment is vital for maintaining the structural integrity and performance of the escalator, and the column line plays a significant role in achieving that.