Abstract: A gate valve (1) is constructed for the simultaneous blocking or clearing of two rectangular passage openings (8,9) of two chamber walls (4,5) that are provided between two vacuum chambers (1,3) and aligned with one another. To this end, it has two valve plates (20, 21), which are a component of a slider (15), which is situated so that it can move with play from a position clearing the passage openings (8,9) to a position which closes the passage openings (8,9). To move the valve plates (20,21) to the closing setting against the passage openings (8,9) on the slider (15), at least one lifting element (24), which is acted on by pressure, is provided.

Abstract: A cover fitted about the periphery of an opening in a chamber wall is provided with a channel having therein both high frequency sealing elements which prevent escape of electromagnetic radiation, and a vacuum sealing element. The HF sealing elements are spaced apart by less than 1/4 of the minimum wavelength .lambda. to be shielded against, and are preferably held in the channel by a profiled element which also holds the vacuum sealing element. Alternatively, the channel may be provided in the chamber wall, or the sealing elements may he held in place without any channel.