A swivelling sliding closure unit includes a stationary refractory plate having a discharge opening and supported by a stationary housing. A swivel pin is fixed to the stationary housing, and a swivel lever having first and second ends is mounted on the swivel pin by a gimbal bearing. A movable refractory plate has therethrough a discharge opening and is supported at the first end of the swivel lever by a movable housing to enable pivoting of the movable refractory plate with respect to the swivel lever. The swivel lever is rotated about the swivel pin to move the movable refractory plate between positions enabling and blocking discharge of molten metal from a metallurgical vessel and also to a replacement position. A rolling element is mounted on the stationary housing, and a raceway formed on the second end of the swivel lever abuts the rolling element. A bracket is hingedly connected to the stationary housing and is connectable to the swivel lever when the swivel lever is in the replacement position thereof. Thereby, upon removal of a clamp which clamps the swivel lever to the swivel pin, the swivel lever may be swung to an open position enabling replacement of the refractory plates.