Level staff
A level staff, also called levelling rod, is a graduated wooden or aluminum rod, used with a levelling instrument to determine the difference in height between points or heights of points above a datum surface.
Rod construction and materials
Levelling rods can be one piece, but many are sectional and can be shortened for storage and transport or lengthened for use. Aluminum rods may be shortened by telescoping sections inside each other, while wooden rod sections can be attached to each other with sliding connections or slip joints, or hinged to fold when not in use.
There are many types of rods, with names that identify the form of the graduations and other characteristics. Markings can be in imperial or metric units. Some rods are graduated on one side only while others are marked on both sides. If marked on both sides, the markings can be identical or can have imperial units on one side and metric on the other.
Reading a rod
In the photograph on the right, both a metric (left) and imperial (right) levelling rod are seen. This is a two-sided aluminum rod, coated white with markings in contrasting colours. The imperial side has a bright yellow background.