An enclosure includes a sidewall defining an opening through which a connector is to extend and a through hole, a resilient piece, and a sliding member slidably received in the through hole. The resilient piece includes a connecting piece slantingly extending from the sidewall between the opening and the through hole and a contacting piece connected to a distal end of the connecting piece. When the connector extends through the opening, The sliding member is slid toward the resilient piece to force the contacting piece to contact the connector.