The convention for defining the sense of circulation and the normal to the surface 'A' is given by the right-hand rule.
The right-hand rule is one common way to relate the three principal directions.
The rotation occurs in the sense prescribed by the right-hand rule.
The direction of B can be found via the right-hand rule.
The surface normal is directed usually by the right-hand rule.
A list of physical quantities whose directions are related by the right-hand rule is given below.
The convention for positive linking number is based on a right-hand rule.
Using the right-hand rule, we expect the curl to be into the page.
The direction of Ω is chosen using the right-hand rule.
Down is chosen as opposed to up in order to comply with the right-hand rule.