A server includes a main board, a side panel having an attached female connector, an expansion card, and a lever. The expansion card includes a latching member having a pivot and a male connector. The lever includes an engaging portion defining a slot, and a main body connected to the engaging portion and pivotally connected to the main board. When the lever is rotated in a first direction, the pivot is slid into the slot, causing the engaging portion to engage with the latching member. Further rotating the lever in the first direction, the expansion card is urged to move toward the side panel until the male connector mate with the female connector. When the lever is rotated in a second direction opposite to the first direction, the expansion card is urged to move away from the side panel, causing the male connector to disengage from the female connector.