Albert Barnes Commentary 2 Kings 16:18

"And the covered way for the sabbath that they had built in the house, and the king`s entry without, turned he unto the house of Jehovah, because of the king of Assyria." — 2 Kings 16:18 (ASV)

The covert ... in the house - This refers to a canopied seat in the temple for the king and his family when they attended public worship on the Sabbath. It was undoubtedly located in the inner court of the temple.

The king’s entry without - This appears to have been a private passage by which the king crossed the outer court to the east gate of the inner court when he visited the temple (Ezekiel 46:1–2).

He turned from the house of the Lord for the king of Assyria - This passage is very obscure. Some translate it as, “he altered [them] in the house of the Lord because of the king of Assyria,” supposing the “covert” and the “passage” were made of rich materials, and that Ahaz took them to supplement his “presents” to the king of Assyria. Others, however, render it, “he removed [them] into the house of the Lord from fear of the king of Assyria.”