Apparatus for attaching internal parts to the interior of a pressure vessel having an inner lining of uncured rubber includes a rigid fastener, preferably an internally threaded nut, rigidly secured over an opening through the wall of the vessel and the rubber lining. A rigid bolt is threaded through the nut from the inside of the vessel so that a lateral shoulder on the bolt is tightened against the rubber lining. A layer of uncured rubber is mounted over the shoulder, and the layer is cured when the inner lining is being cured to embed the shoulder in the rubber and seal the bolt against leakage. Internal parts are attached to the portion of the bolt inside the vessel, and the structural load applied to the bolt by the internal parts is transmitted to the wall of the vessel through the rigid bolt and nut.