Put the melon pots against the wall or rail where you plant to build the trellis. Make sure that the plants still get full sunshine for six to eight hours a day, with good air movement for pollination.
Cut a length of trellis netting the height and length of the balcony wall or railing. Put the netting against the wall or railing behind the melon pots and use hammer and nails or a staple gun to secure the netting to the wall or railing. Space the staples or nails at every 3 to 4 inches to build the most secure trellis.
Tie the melon vines up to the netting to train them up and out for best air and sun exposure. Tie only main vines, and keep the ties loose to avoid damaging the plants.