Danielli.capture/Shutterstock If you ever find yourself questioning how certain elements of your car function, such as how electronic parking brakes work , then you may wonder what the lines your vehicle's back glass are for. Not all cars have this feature, but, today, most do. The lines are usually horizontal but can also be in a grid pattern, and without them you might have difficulties driving safely, especially in inclement weather. That's because they're crucial elements of your vehicle's defrosting system, referred to as the rear defroster.  While the front windshield defroster is part of the car's HVAC system and blows hot air through vents on top of the instrument panel to clear ice and fog, the rear defroster uses electrical current to produce heat to clear the back window. The lines are actually thin wires made out of conductive materials like metal or electrically conductive resins, and they are either attached to the inside of the glass or embedded within the glass during manufacturing.…