From Manners and Customs of the Bible:
2 Kings 20:11. Isaiah the prophet cried unto the Lord: and he brought the shadow ten degrees backward, by which it had gone down in the dial of Ahaz.
Maaloth, “dial,” is the same word that is rendered “degrees” in this verse, and “stairs” in 2 Kings 9:13. This and the parallel passage in Isaiah 38:8, are the only places where the word “dial” occurs. Our translators probably judged correctly in supposing from the context that by maaloth in this place some instrument for measuring time is meant; but what was its peculiar shape is left to conjecture. The Babylonians were doubtless the originators of the sun-dial. Herodotus states that the Greeks derived it from them (Euterpe, chap. 109), and it is highly probable that king Ahaz, after whom this dial in the palace court was named, obtained the idea from Babylon.
Some think this dial was a hemispherical cavity in a horizontal square stone, with the gnomon in the middle, the shadow of which, falling on different lines cut in the hollow surface, marked the hours of the day. Others imagine a vertical index surrounded by twelve concentric lines. It may have been, as some suppose, a pillar set up in an open elevated place, with encircling steps on which the shadows fell; or stairs so constructed that the shadow of an obelisk or of a gnomon on the top platform might indicate the hours.
The “degrees,” however, must have marked shorter periods than hours, since ten forward and ten backward are spoken of as only a part of the whole number of degrees. See KEIL, Commentary, in loco.
It has been suggested that the “stairs” from which Jehu was proclaimed king, as recorded in 2 Kings 9:13, were the same as the “dial” of Ahaz. As already noted, the same word, maaloth, represents both. The idea is that Jehu was taken up the different steps of the dial until he reached the top platform, where he was placed by the aide of the gnomon, when the trumpets were blown and the formal announcement was made, “Jehu is king.” See Clarke, Commentary on 2 Kings 9:13