Diptych triptych form, with two outer panels that could be closed across the main central representation. They are one type of the multi-panel forms of painting known as "polyptychs". The diptych was a common format in Early Netherlandish painting and depicted subjects ranging from secular portraiture to religious personages and stories. Often a portrait and a Madonna and Child had a leaf each. It was especially popular in the 15th and 16th centuries. Painters such as Jan van Eyck, Rogier van der Weyden, Hans Memling and Hugo van der Goes used the form. Some modern artists have used the term in
Hinged expansion joint joints used in piping systems are restricted to pure angular rotation by its hinges. As a pair, hinged expansion joints will function together to absorb lateral deflection. Advantages of hinged expansion joints are that they are typically compact in size and structurally rigid. Hinged expansion joint A hinged expansion joint is a metallic assembly, that can rotate in a single plane, used to absorb changes resulting from piping thermal expansion or contraction. They include hinges, attached to the expansion joint ends with a pair of pins, which allow angular movement in a single plane, restrain the pressure thrust, and prevent