An improved rail includes two side portions, and a mid portion interconnected between the two side portions. The mid portion and the two side portions form a component that defines three sides of a transceiver module space. The rail further includes a blocking structure coupled to the component. The blocking structure is adapted to (i) permit a connecting portion of a transceiver module to connect with a connector when the transceiver module engages the rail and moves into the transceiver module space toward the connector and when a circuit board side of the transceiver module faces the printed circuit board, and (ii) prevent the transceiver module from contacting the connector when the transceiver module engages the rail and moves into the transceiver module space toward the connector and when a heat dissipation side of the transceiver module faces the printed circuit board.