To ensure that the shafts were vertical, Romans hung a plumb line from a rod placed across the top of each shaft and made sure that the weight at the end of it hung in the center of the shaft.

为确保竖井垂直，罗马人在横跨每个竖井顶部的杆上悬挂一条铅垂线， 并确保其末端的重物悬挂在竖井的中心。