The skid in a stylus type roughness measuring instrument is used to provide ............ A .............. and define ................... B .............. geometrical profile of the surface.

$$A.$$ support / datum
$$B.$$ micro / macro

Abbe's principle of alignment states that the scale axis must coincide with the line of

Outside micrometer is calibrated with the help of

For angle measurement in metrology, the following pair can be used in conjunction with each other