Determination of straightness error using spirit level

[@thekkemavila]

Suppose the error is higher than the maximum division marked on the precision level then can we use feeler gauge on bottom of the precision level and caculate.if so can you tell me the caculation

[@thekkemavila]

Is this calculation as per the mathematic rules.calculation is simple but where from did you get.can you give the references

[@thekkemavila]

If we use a straight edge should we need to take each portion of the length or can we place the precision level on the center of straight edge and take the reading

[@thekkemavila]

What is the base of your caculation

[@mallikarjunbillur6362]

Sir I would like to know how to calculate last but second column

[@debayan7]

Nothing can be understood from ur video

[@debendrachattar4239]

I can't understand

[@ashutoshsingh1137]

Sir master level cal culation