keystone

A keystone is a polyurethane decorative element placed at the very centre top of an arch, completing and emphasising the arch line. On window and door arches and facade arches it is used to highlight the centre point of the arch. It is mostly in a trapezoidal or console form that widens downward. Polyurethane is lightweight and applied directly over the arch with mounting adhesive; it resists moisture and impact, does not crack or blister, and is paintable. Being much lighter than a real stone keystone, it is easy to install even on high facades. Being mould-cast, all keystones share the same form and detail. Polure produces the keystone in different height and width sizes.