Page "Magnetism" Paragraph 72

One tool for determining the direction of the velocity vector of a moving charge, the magnetic field, and the force exerted is labeling the index finger " V ", the middle finger " B ", and the thumb " F " with your right hand.

When making a gun-like configuration, with the middle finger crossing under the index finger, the fingers represent the velocity vector, magnetic field vector, and force vector, respectively.

See also right hand rule.