An enclosure comprises a chassis, a side panel and a knob structure. The chassis comprises a rear panel in which a latching hole is defined. The knob structure comprises a mounting member, a sliding member engaged in the mounting member, a positioning member secured to the side panel and a resilient member elastically engaged between the sliding member and the positioning portion. The mounting member is secured to the side panel. The sliding member comprises a hook. The sliding member can slide from a first position to a second position; when the sliding member is in the first position, the hook engages in the latching hole, when the sliding member is in the second position, the hook disengages from the latching hole; the resilient member elastically deforms to bias the sliding member to slide from the first position to the second position.