There have been several question over the years about line locks and other brake locking products. I have used this Mico unit on my Jeep for 10 years without any problems.I also use a Hurst Roll Control (line lock) and both these units are plumbed into the front brake system. I tried to install it into the rear brake system but it wouldn't fully lock, something to do with the brake proportioning valve I was told.
I bought this unit ( part # 02-620-002) from 6-States Supply but I read somewhere that NAPA offers a similar unit.
Here is an install on a GMC motorhome
The following scans are of the instructions for the Mico unit I installed in my Jeep. They are reduced in size and I would be glad to e-mail a full size scan to anyone if desired.
Note: These are designed as brake system supplements only and NOT to be used In the place of the OEM parking brake system.
The Mico brake lock switch is mounted above the light switch under a protective cover.
The Hurst Roll Control switch is the red button in the shifter handle.