Driveshafts are built with the yokes at each end of the tube aligned. If the yokes are not aligned, the driveshaft is phased incorrectly. Driveshafts will always have all yokes aligned. Failure to phase and align a driveshaft properly will result in vibrations that will destroy the driveshaft, dyno, and/or engine, and improper phasing can cause serious bodily harm when the driveshaft reaches its failure point. Be smart. Be SAFE.