Round Frames Fitted with Convex Mirrors - An Insight. The method for making round wooden frames is associated with Shipwrights of the late middle-ages, who were tasked with carving the ships round wheel. Few people realise the difficulties even the most experienced carpenter still faces when building a round frame; the reason behind why so few companies attempt to specialise in making them. At Benson Karim, our convex mirrored glass is hand cast and silvered in our studio glass works, just as tradition dictates. In no other way would we be able to produce mirrors which improve on the detail and beauty of an 18th century masterpiece.Convex mirrored glass became popular in England and America during the 18th and 19th centuries. The Butler's Mirror, popularised by English Gentry, and was used to summon a servant's attendance. These mirrors have the characteristics of a fish eye lens, and when cleverly positioned allows any gesture to be seen, even from around a corner.