A male 25 years old presents to the dental clinic with a black spot. He also gives the history of previous dental treatments of other teeth as well and wants gold to be filled in his tooth. On examination, it is revealed that 16 no. tooth has pit and fissure caries. Which preparation is used for retention in this restoration?
Skirts.
  Skirts are preparation features used in cast gold restorations that extend the preparation around some, if not all, of the line angles of the tooth. When properly prepared, skirts provide additional, opposing vertical walls that increase retention of the restoration. The placement of skirts also enables increased resistance to fracture by allowing the envelopment of the remaining compromised tooth structure with the restorative material.
Sturdevant operative dentistry  7th  E D I T I O N, Page No:131
Vertically oriented grooves
Horizontally oriented grooves
Coves
Skirts