R.L of Bench mark + Back sight reading
R.L of Bench mark ? I.S reading
R.L of Bench mark ? F.S reading
R.L of Bench mark ? Back sight reading
The line of collimation
Horizontal line
Vertical line
Slant line
One
Two
Three
Four
Horizontal surface
Vertical surface
Level surface
Curved surface
Curved line
Level line