A chassis-mounted round baler particularly useful with an on-board cotton module building system includes a bale release gate frame section connected to a forward frame section by a four bar linkage to define a gate path that allows the folding of the baler into both field transport and shipping configurations while maintaining desirable operating, transport and shipping heights. The gate linkage incorporates a self latching feature wherein a small vertical movement of the gate as the gate cylinders are operated releases a gate latch member from a forward frame member during gate opening and reengages the gate latch with the forward frame member during closing. The gate interacts with the bale handler to provide a stop for the baler gate when the baler gate is placed into a cradle on the handler.