No its not a line lock. Its a parking brake you plumb inline to your rear brakes. I had one on my B2 and it worked great. Putting it on my truggy next
http://www.speedwaymotors.com/Park-Lok-Hydraulic-Brake,1970.html
http://www.speedwaymotors.com/Park-Lok-Hydraulic-Brake,1970.html