Plug is designed to finish of an open end of 136 x 80 mm Compact Polymer Grate and Channel with a little more robust plug than what the manufacturer produces. It fits into the “U” clip end of the channel.

As it is outside I printed in PETG however ASA or ABS would also be suitable. Supports on the build plate will be required and 0.2mm layers with a 0.4mm nozzle will suffice and I would set perimeters to >3 and infill to 25% for strength.