Based on clinical observations, Vera & Gutierrez (2004) reported that when using the ElementsTM Diagnostic Unit the file should be withdrawn to the 0.5 mm mark instead of the 0.0 mm mark to achieve the accurate identification of the apical constriction that they assumed should be 0.5 mm short of the external (major) foramen. Therefore, taking the file to the 0.0 mark on the display and then withdrawing it 0.5 mm appears to be the most accurate way to