Abstract: A moulding apparatus including a pair of mould cavities with locking spue grooves, means to form moulded rubber article parts in the cavities, means to prework the rubber without substantial curing before it is formed, means to pressurize the mould with gas and means to bring the mould cavities together to join the article parts. The arrangement for pressurizing the mould includes a retractable casing which is movable between a position in which the mould cavities are enclosed to permit their pressurization and a position in which the cavities are accessible outside the casing.