Abstract: A holder for receiving dental root canal instruments consists of two circular plates arranged in coaxial spaced-apart disposition, one plate having a series of through holes therein each to receive a respective instrument with the tip thereof resting on the other plate the separation of the two plates, and thus the distance between that plate face which receives an instrument tip and the corresponding face of the other plate, being selectively adjustable to provide a datum for setting indicators on the respective instruments mounted on the holder.