Quick answer
Thinking beats fortification. One man with sense gets over a wall that an army was built to stop.
Read both lines
The NKJV footnotes "scales" as climbs over the walls of, which makes the picture concrete: the wise man is not besieging, he is getting in. The second line names what actually falls, and the word order in Hebrew puts the emphasis on trust rather than on stone. It is the confidence the stronghold produced that comes down, which is a sharper claim than saying the wall did. The book has said something adjacent at 24:5, that a wise man is strong. Here it goes further and says that where strength and wisdom meet directly, wisdom is the one that arrives on the other side. Ecclesiastes tells the story version, of a poor wise man who single-handedly delivered a besieged city and whom nobody afterward remembered (9:14–16). That ending is worth keeping attached to this verse. Wisdom wins and is not always thanked for it.
Related: Proverbs 24:5–6 · Proverbs 20:18 · Ecclesiastes 9:14–16 · Proverbs 16:32
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.