Operational steps: 1. Establish a straight channel for the dental crown.

2. Use 10# and 15# hand K-files to clear the root canal and explore it.

3. Use S1 to enlarge the crown part, and SX if necessary, with the depth not exceeding that of 15# K-file. The recommended speed is 300 rpm.

4. Use 15# K-file to measure and determine the working length.

5. Sequentially use S1, S2, and F1, each time briefly lifting after every 1-2 mm until the file can no longer descend (i.e., prepared to the working length), all under the soaking of the irrigation solution.

6. Use F2 (recommended as the smallest root tip preparation instrument) to prepare to the working length, then perform a straight measurement at the root constriction.

7. For large root canals, use F3 to prepare to the working length.