Lorentz force FBI tool

Remember the left hand rule (a.k.a. FBI rule) to work out the direction of the Lorentz force as a result of a current flowing through a magnetic field? Or maybe you're in high school struggling with it at the moment? You'll find that sometimes Physics exams will have you strain your left wrist to solve questions on the Lorentz force.

Tutoring people in high school I saw that this can be a real pain and a source of frustration. That's when I came up with the FBI tool. You slide the tool onto a pencil, point the pencil in the direction of the current, turn it to have the B arrow point in the direction of the magnetic field and F will point in the direction of the force. Easy, simple, clean, without breaking a sweat or a wrist.