In a Japanese garden, a rustic wooden picket fence can be used to create a sense of enclosure and privacy. The fence can be designed with a gate or an arched entrance, adding an element of mystery and intrigue. It can be stained in a dark color to blend with the natural elements of the garden. The picket fence serves as a backdrop for carefully placed rocks, lanterns, and bonsai trees, enhancing the serene and contemplative atmosphere.