The invention relates to a device (10) for at least partially closing an opening (5) of a cooking vessel (2), having a support element (11) which can be brought to rest on an opening edge (6) of the opening (5) of the cooking vessel (2), and a plug-in element (12) which can be inserted at least partially through the opening (5), characterized in that the plug-in element (12) has a locking means (13) which can be brought into a locking position (I) in which the locking means (13) interacts with the opening edge (6), so that pulling out (205) of the plug-in element (12) is prevented.