Individual insulation layers are stuck on the pins and fixed using installation discs. The last insulation layer is fixed using a twist clip. In applications involving high temperatures the twist clip is replaced by a ceramic component, the Cuplock. This prevents gases from the furnace corroding the exposed ends of the fibre fixing pins and the twist clips. The end of the locking pin is in the Cuplock and therefore stands back from the hot side of the lining; it is protected by a fibre mastic plug which closes the cuplock opening. We use an improved shape of the internal part of the Cuplock element with a tapered conical edge, which prevents the mastic plug from falling out when it shrinks.