It sounds like you are describing how to measure cylinder bores with a dial bore gage. You pretty much have it correct.
The bore gage must always be read at the largest reading whether you rock it back and forth or not. If it is kept parallel with the cylinder it isn't necessary to rock it back and forth.
The cylinder must be checked at all points , but experience and practise will show you where the largest part is always. Most times it is just where the top piston ring stops perpendicular to the crankshaft.
I don't prefer or recommend this way ", someone told me I had to take the indicator on the point you've reset the indicator , rotate the indicator 90 degrees from there. Take this measure without ' swinging' left and right the indicator. I thought that i need to
' swinging' ." You may not get a good reading since bore gages are not designed to be rotated. You can rotate first then swing back and forth though.
I hope this helps you. I have trouble with your english a little bit.
