Figure depicts:

Anticurvature Filing This technique is designed to keep files away from the furcational zone of curved root canals thus preventing excessive removal of dentin and strip perforations at this critical zone. This goal should be achieved by use of precurved instruments (files) at the outer side of the curvature. When the file can be easily negotiated around the ledge, anticurvature filing will enable the clinician to blend the ledge into the canal preparation.