It would have been almost impossible for Noah and his sons to construct the Ark in the time they did with the assistance of only two hands apiece.
Think, however, of how fast they could work with the assistance of that third arm.

Noah could hammer a clapboard on to the Ark with two hands while grasping a saw and cutting a new board or planing it off with his tail.

So with the others.

We all know how much a third hand would help us at times." "But how do you account for its disappearance ?" put in Doctor Livingstone.

"Is it likely they would dispense with such a useful adjunct ?" "No, it isn't; but there are various ways of accounting for its loss," said Munchausen.