K Rails at Canadian Border

Several years ago I entered the US (Washington) from Canada with my 30 foot 5er and had to negotiate around K Rails. Did I come in the wrong line? Is there an RV line/Semi line/Huge motorhome line that would have avoided the K Rails. I only had a 30 foot 5er too. I couldn't imagine someone with a 38 foot 5er with a long bed truck.

Jason