Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Ground Event / Encounter Other / Unknown; Ground Excursion Runway
Air Traffic Control Issued Advisory / Alert
Chart Or Publication; Human Factors; Airport
There is construction taking place on the approach end of runway 14 at RAP. The runway is shortened 1550 feet. To utilize all of the available runway a back taxi is required due to a closed taxiway. We taxied out to runway 14 via taxiway T1 and taxiway Alpha. We were then cleared to back taxi runway 14.  There is a displaced threshold with the construction and it was closed for taxi operations. I turned around on the wrong side of the displaced threshold line. Tower informed us of that error and cleared us for takeoff.
We need a special airport page for this airport. If that portion of the runway is not for use they could bring the barricades up to the threshold line to help us see it's closed.
Forced by airport construction to back taxi on Runway 32 to utilize the full remaining length of 14 an air carrier flight crew taxied beyond the temporary displaced threshold prior to reversing course.  The Tower reminded them of their technical 'violation' and cleared them for takeoff.