Which preparation is used for retention in the incisal area of Class III amalgam?
Retention Grooves and Coves:
Vertically oriented grooves associated with the facial and lingual aspects of a proximal preparation are used to provide additional retention for the proximal portions of some Class II amalgam restorations. Horizontally oriented retention grooves are prepared in most Class III and V preparations for amalgam and in some root-surface tooth preparations for amalgam and composite resin. Small retentive indendations, referred to as “coves,” are utilized for retention in the incisal areas of Class III amalgams.
Reference: Sturdevant operative dentistry. 7th EDITION, Page No:131
Vertically  oriented  grooves
Horizontally oriented grooves
Coves
Skirts