Measured and theoretical strand elongations don't agree within 5%. Now what? Measured and theoretical elongations must agree within plus-or-minus 5% when pretensioning strands for prestressed operations. In a well-run plant, the measurements usually fall within the 5% tolerance. But when differences occur, there are several areas to check to make the appropriate adjustments. If the tolerance difference is not corrected, serious structural consequences might occur, resulting in an unacceptable final product. Prestressed producers offer advice on where to look, and manufacturers describe products that will help to avoid this critical problem.