Accurate and a reproducible working length is an important factor in root canal treatment. It establishes the apical limit of the canal preparation and demarcates the creation of an apical stop. It also enables thorough debridement of the canal, allowing it to be performed without over instrumentation, trauma to the periapical tissues or destruction of the anatomy of the root apex. It establishes the apical limit for obturation. The success rate of conventional root canal treatment has been correlated with the length of the final root canal filling.