A lock mechanism within a slot of a computer chassis is disclosed. The lock mechanism includes a gear wheel, a gear rack body, a push rod latch, a push rod body, and a chassis latch. The gear wheel, the gear rack body, the push rod latch, the push rod body, and the chassis latch cooperate to restrict a flap in the slot from opening when the flap is in the closed position, and the chassis latch is engaged with a cutout on the push rod body.