38) Which level is that the line of sight remains horizontal once the operator has roughly levelled the instruments?

39) How many level screws are used to level the instruments?

40) How to eliminate parallel between the staff and reticle in auto level?

41) What is the gap of stems of ?E? or 3 between them of earth?

42) What is the level that is widely used in construction work but not for more precise control work?