How do you install a horizontal fence on a slope?

While many horizontal fences can be installed on a slope, consider that one of the design attributes of a horizontal fence is to provide a leveled appearance and a continuation of landscaping with a nod towards the Earth's horizon. In contemporary architecture, horizontal fences follow the concept of "clean lines" which evoke a sense of space and simplicity. Having said that, personal preferences towards horizontally flowing lines that follow the slope of the ground may be more appealing than staying parallel to the Earth's horizon. In either case, a component-built fence can easily be adapted to install a horizontal fence on a slope. For example, Trex with the Horizons fence system can be built on a slope by cutting the pickets and horizontal rails. The most efficient approach is to set up a jig on sawhorses so you can cut all of the pickets per section at the same angle.  The top and bottom frame rails will need to be cut on the appropriate angle and should be touched up with rust-inhibiting black matte paint.