How to Disconnect a Jumper

Stupid question. I brought that Arduino Motor Shield R3 http://arduino.cc/de/Main/ArduinoMotorShieldR3and want to use external power (12V). Therefore I need to "disconnect" the jumper from the back http://arduino.cc/de/uploads/Main/MotorShield_R3_Back.jpg of the shield. But how do I do that? Do I need to solder that? I read somebody scraped it out. Is this the way?

You use a sharp knife and cut away the small track. You put a solder blob on it to connect it back.