Are you referring to a Time Away from Base (TAFB) rig?? Also known as a trip rig?

It's a guaranteed pay ratio for time spend "on the road" working. SkyWest now has a 4:1 trip rig. This means that for every 4 hours you are away from base "working" regardless of whether your on duty or not (think sleeping in a hotel somewhere), you are guaranteed 1 hour of pay.