Please ensure that the enclosure is suitible for your animals, that should live in it, especially that the ventilation is sufficient.
The ventilation slots are 1 mm wide, so check that your animals can't fit through ;-)
The frames are designed to hold four 20x15 cm (acrylic-) glass plates with a thickness of 2mm, which are usually availabe off the shelf. These will also provide the most of the stability, since it is designed to use less material for printing.
If acryilic glass is used I recommend to use a deburrer at the left and right edges to get it fit smoother. If a backwall is needed i.e. a non-transparent acryilic sheet can be inserted.
The author hasn't provided the model origin yet.