A border is easy to add with a pencil. On a real deck, it asks questions about what is underneath, where the boards end, and how the joints move. It is a layout choice wearing the clothes of a decoration.
Draw the entire board pattern
Show board directions, available lengths, end joints, borders, stairs, and any breaker boards. A perimeter detail that looks tidy on one edge may produce an awkward narrow strip at the other. Work through the pattern before ordering.
A same-colour border can finish the edge quietly. A contrasting one makes the outline more prominent. Both can look good; neither makes an undersized dining area more useful. Resolve the deck’s shape before accentuating it.
Ask what supports the ends
Trex’s picture-framing guide shows additional framing and support associated with the border. Use the current instructions for your exact decking product, including fastening, spacing, and edge requirements.
On an existing deck, do not assume the frame can accept a border because the surface boards can be cut shorter. The proposed board ends and border need appropriate support, and the underlying frame needs to be suitable for continued use.
Approve one complete corner
Ask to see a drawn corner with the fascia, board ends, fasteners, and joints together. Choose the border if that detail improves the finished deck enough to justify its work. Choose a simpler layout if the material already makes an attractive edge. Good finishing is a resolved detail, not a compulsory extra stripe.