(Figure 12.2) In a properly adjusted dumpy level, desired relations among fundamental lines are
Axis of the level tube is perpendicular to the Vertical axis
Horizontal cross hair should lie in a plane perpendicular to the Vertical axis, so that it will lie in a Horizontal plane when the instrument is properly leveled.
The Line of sight is parallel to the axis of the level tube.
Also, the optical axis, the axis of the objective lens and the line of sight should coincide.