Abstract: A method of cladding a separator, that is a diaphragm or membrane, to a cathode box of the pocket type comprising a plurality of foraminate walls, the method comprising positioning a separator in the form of a sleeve in each pocket of the cathode box with the ends of the sleeves projecting beyond the ends of the pockets, placing a first sheet material in contact with those parts of the sleeves projecting beyond the ends of the pockets in one direction and sealing the sleeves to the sheet material, placing a second sheet material in contact with those parts of the sleeves projecting beyond the ends of the pockets in the opposite direction and sealing the sleeves to the second sheet material, and removing those parts of the sheet materials adjacent to the ends of the pockets. Also a cathode box clad with separator, and an electrolytic cell comprising a cathode box clad with separator.