Round Decklight 5.1/2" Diameter with Stainless Steel Frame
From the early 1900s, Davey & Company has been producing a range of deck prisms to bring natural light down below. Manufactured in England these prisms are solid glass with either flat frames, where the glass is rabetted in, or deep frames for thinner decks. In both cases a marine quality black mastic should be used such as a polysulphide or synthetic rubber and to improve adhesion the glass should be abraded first where the sealant touches.
In this style the glass is set first into the deck using a marine quality mastic and then a flat frame is positioned over the rim of the glass and screwed down. This is only suitable where there is sufficient depth of wood to support the weight of anyone walking on it.