Abstract: A walk-through flat barn parlor comprises a number of modular stalls for managing dairy cows. Each module has a frame to which a pair of gates are mounted. The axes of rotation for the gates make compound angles with the vertical such that the gates are biased by gravity to rotate from a closed mode to a ready open mode. A control mechanism is actuated by a cable mechanism from a milking station to unlock the gates for automatic rotation by gravity from the closed mode to the ready open mode. A cow walks to the ready open gates and pushes them to the closed mode, where she is constrained for milking. After completion of milking, the farmer actuates the cable mechanism to unlock the gates and enable the cow to push them to an exit open mode. When the cow has cleared the gates, they automatically rotate by gravity back toward the closed mode. A pawl on a bar connecting the gates co-acts with the control mechanism to enable the gates to rotate past the closed mode all the way to the ready open mode.