Joining coroplast

Make sure the cuts (sides you want to join) are square. Use clear packing tape on the underside. Then I'd use clear packing tape on the inside, being careful to get a good flat smooth lay to it. I wouldn't try to do a whole piece of tape up the sides. My experience is no matter how good you try to get it, there is a little play in the bend of the tape that gets bedding caught in it and makes it harder to clean.