cold shut
Webster's Dictionary (GCIDE)
Shut \Shut\, n. The act or time of shutting; close; as, the shut of a door. [1913 Webster]
Just then returned at shut of evening flowers. --Milton. [1913 Webster]
2.A door or cover; a shutter. [Obs.] --Sir I. Newton. [1913 Webster]
3.The line or place where two pieces of metal are united by welding. [1913 Webster]
Cold shut, the imperfection in a casting caused by the flowing of liquid metal upon partially chilled metal; also, the imperfect weld in a forging caused by the inadequate heat of one surface under working. [1913 Webster]