Abstract: The present invention relates to a side piece for spectacle frame, adapted to take a normal position with slight horizontal clearance and a firm holding position in which the curved rear tip is applied against the ear, wherein said side piece is formed by a sheath in which slides a piece which is urged by a spring in the direction of the lens-bearing face and which is normally immobilised by a blade abutting against a fixed socket. A push button enables the piece to be released when desired. The invention is more particularly applicable to the spectacle or sunglasses industry.