The Egg & Dart collection from Nostalgic Warehouse is characterised by a repeating pattern of an Egg shape followed by a Dart or Arrow shape, and traces back to Ancient Greek architecture as evidenced by the Erechtheum, a temple on the north side of the Acropolis in Athens. The styling was also popular with the Romans and has been used in classical architecture in Europe since the Renaissance. As Greek Revival swept across the United States in the 18th and 19th centuries, it reappeared in the early 1900's and was the rage for decades. The Egg & Dart collection is loosely based on Yale & Towne's Miletus door set from the early 20th century.The interior half only option is to be ordered in conjunction with an "exterior handle only" door set. This option is made available for those who want a different style or finish on the interior and exterior of their entry door. A double cylinder will have two keyed deadbolts (one interior, one exterior) while a single cylinder will have one keyed deadbolt (exterior) with a thumbturn on the interior.