Before the introduction of the euro, francs were also used in France, Belgium and Luxembourg, while Andorra and Monaco accepted the French franc as legal tender (Monegasque franc).
Inside the caliper is a brake pad, a small block of friction material backed with a metal plate. When you step on your brake pedal, pistons inside the caliper cause it to apply pressure to the brake pad which squeezes the rotor, causing the car to slow or stop.
The caliper is what does the clamping to tighten the pads against the rotors and stop the vehicle. Tools needed for this job: Jack and jack stands, 5/16, 3/8, 10mm, 1/2, 3/4 or 7/8 (depending on lug nut size), 18mm sockets and socket wrench, a flat-head screwdriver (comes in handy for many different things!).