A device for feeding suction air or blowing air to a sheet-retaining device displaceable relative to a machine element in a sheet-processing machine, includes a first air-feeding element connectible in terms of flow to a suction-air or blowing-air source. A second air-feeding element cooperates telescopically with the first air-feeding element for forming an air through-passage duct connected in terms of flow to the sheet-retaining device.