As for the flap that is left over from the tent curtains, the leftover half curtain is to hang down over the back of the tabernacle.

"[The] wings of [the] female ostrich flap-- [are they] [the] pinions of [the] stork or [the] falcon?

And my hand hath found as a nest the wealth of the peoples, And as the gathering of eggs that are forsaken, all the earth, have, I, gathered, - And there was none to flap a wing, or open a mouth or chirp.