bifold

A door, window, shutter, or divider consisting of two equal panels hinged together so that it opens by folding the panels against each other.

A sheet of paper or cardboard folded in half along a crease down the center.

A wallet, billfold, or carrying case with a single fold, so that it opens like a book.

A crease or turn that causes something to double back on itself.

Twofold, double.

Of two kinds.