When installing a one-sided fence, the smooth or finished face is traditionally directed toward the neighboring property or public street. The side showing posts, rails, and other structural supports remains facing the person who owns the fence.
Part of the reason is simple courtesy. Since the property owner chooses to build the fence, neighbors should not be forced to look at its rougher, unfinished side. A finished surface also creates a cleaner appearance from the street and can help the entire neighborhood look more attractive.
Keeping the rails on your own side may also improve security. Horizontal supports can act like steps, potentially making the fence easier to climb from whichever side they face.
Double-sided or “good-neighbor” fences solve the appearance issue by looking finished from both properties. They often cost more, but each household receives an attractive view.
Before building, confirm the property boundary and discuss the project with the neighbor. The image’s advice is a widely accepted rule, but it is not universal law everywhere.