The bubble tube is nearly filled with ............

Handles of chains are made up of ............

A plumb bob is required ............

A contour map of the area is essential before proceeding with the construction of ............

"Cross-section" and "Longitudinal sectioning" is ............

The angle between two plane mirrors of optical square is ............

Chain survey method is most suitable ............

The obstacle, which obstructs chaining but not vision is a ............

Long offsets are taken if the offset length exceeds ............