My good friend always puts the line lock on the Rear Tires not the front cause they never really hold the car still unless you have your foot on the pedal.
Turn line lock on, hit the button which locks out pressure to the REAR brakes. Pump up the pedal and do your burn out. This way you are using the pedal pressure to hold the car on the front brakes which will actually hold the car from moving. You are using the Line lock to BLOCK brake fluid from reaching the Rear Brakes.