Canst thou with him spread out the sky, Which is strong as a molten mirror? (ASV)
By the above Pro theory, you must also believe that the ancients really believed that there were flying jugs in the sky (Job 38:37). Hence, this is nothing but a metaphorical expression.
Edit this section to note miscellaneous facts.
Job 38:37 "Who has the wisdom to count the clouds? Who can tip over the water jars of the heavens"
This does not seem to refer to flying jugs, but another reference to the heavens being a solid structure, or firmament, and a holder of water.