The opening window came late to domestic architecture. The first windows were unglazed wooden shutters, sliding sideways. Only the Big House had hinged, lead-light windows on an iron-frame held shut with a small catch fixed to the frame and a hook-and-eye stay. As glass became cheap enough for widespread use it was first used to glaze the old sliding shutters. Next was the sash window, sliding up and down, with a complicated system of pulleys and counter weights.
By the time today’s outward-opening hinged windows became the standard, there were butt hinges to provide the opening mechanism and many ways of making up the universal joint required for a stay to keep them open, wide or just a ventilation crack.
The catch too required a little engineering, because the early wooden frames were subject to warping and the corner joints held only with pegs primitive glue-pot glue and the catch had to pull the casement into place. Again several mechanisms were tried, until the wedge-shaped mortise plate, used by Forgeries, became widely accepted.