- A rule for determining polarity produced by flowing electric current.
- rule of thumb to envision the orientation of nut movement on a bolt to loosen/tighten it. Right thumb points along threaded shaft; direction of fist opening shows direction of nut loosening.
- A rule stating that if the thumb of a right hand is oriented along the same axis as the current flow through a conducting wire, that the fingers of this hand will curl along the same direction as the magnetic field produced by the wire.
- For a conducting wire moving through a magnetic field, a rule stating that if the middle finger, index finger, and thumb of a left hand are extended at right angles to each other, that the middle finger will indicate the current flow, the index finger the direction of the magnetic field, and the thumb will indicate the direction of the movement of the wire. This rule also applies if the conducting wire is substituted by an electron beam.