A casing apparatus, comprising: a waveguide having a wall which is designed for guiding an electromagnetic wave of a predefinable wavelength and which comprises an edge face extending substantially perpendicularly to the direction of propagation of an electromagnetic wave guided by the waveguide; a wall device; a protection device having a bearing surface; wherein the wall device is designed to absorb and/or exert a force which acts substantially perpendicularly to the direction of propagation of the electromagnetic wave; wherein the wall device is formed as an antenna device (503, 507) at least in part, such that the waveguide transitions into the antenna device, wherein the antenna device is separated from the waveguide by the protection device; wherein the antenna device has a process cut-off and/or a filling at one end; wherein the protection device protects against the penetration of particles from an antenna device into the waveguide; characterized in that the protection device is arranged at one end of the waveguide in a way that the said protection device absorbs and/or exerts a force oriented substantially perpendicularly to the direction of propagation of the electromagnetic wave, such that the bearing surface of the protection device keeps in contact with the edge face of the waveguide; wherein the protection device is arranged between the waveguide and the antenna device and comprises a snap lock for fixing the protection device to the end of the waveguide; wherein a wall area of the wall device bears against the snap lock; wherein the wall of the waveguide comprises corresponding sockets in which snap lock devices formed as bracket can engage. a waveguide having a wall which is designed for guiding an electromagnetic wave of a predefinable wavelength and which comprises an edge face extending substantially perpendicularly to the direction of propagation of an electromagnetic wave guided by the waveguide; a wall device; a protection device having a bearing surface; wherein the wall device is designed to absorb and/or exert a force which acts substantially perpendicularly to the direction of propagation of the electromagnetic wave; wherein the wall device is formed as an antenna device (503, 507) at least in part, such that the waveguide transitions into the antenna device, wherein the antenna device is separated from the waveguide by the protection device; wherein the antenna device has a process cut-off and/or a filling at one end; wherein the protection device protects against the penetration of particles from an antenna device into the waveguide; characterized in that the protection device is arranged at one end of the waveguide in a way that the said protection device absorbs and/or exerts a force oriented substantially perpendicularly to the direction of propagation of the electromagnetic wave, such that the bearing surface of the protection device keeps in contact with the edge face of the waveguide; wherein the protection device is arranged between the waveguide and the antenna device and comprises a snap lock for fixing the protection device to the end of the waveguide; wherein a wall area of the wall device bears against the snap lock; wherein the wall of the waveguide comprises corresponding sockets in which snap lock devices formed as bracket can engage.