Protractor measuring
Rules and angles
For protractor measuring with 1° accuracy protractors
with graduations in integer grades are used. For more
accurate measuring than integer grades a bevel vernier
protrator is used.

Planetary and squareness control
When controlling planetary and squareness rules or
squares are used. There are both rules and squares
with different tolerances. The most accurate types are
knife edge rules and knife edge squares which have a
knife edge formed black coloured edge for better contrast
effect.
When using you see a light gap between the work
piece and the measuring tool. By using a thickness
gauge you can feel how rough a surface is or how high
the angular error is.

Gauge blocks

To calibrate or reset measuring equipment, measuring
fixing devices or gauge, gauge blocks are
used. Also when adjusting tools and machines gauge
blocks are used. Gauge blocks are blocks manufactured
with a high dimensional accuracy, planetary
and parallelism. By surface roughness the gauge
blocks can obtain a very high adhesive strength
when the blocks are turned and pressed together.
That is how gauge block combinations are put together
so that the total measurement value of all
blocks is equal to the total length.