Quick answer
The prudent man's knowledge shows up in what he does. The fool's folly shows up too, and he is the one displaying it.
Read both lines
The contrast is between two kinds of visibility. Prudence appears as action informed by something, so you learn what a careful person knows by watching what they do. Folly appears as exhibition, and the verb suggests spreading something out where it can be seen. This is the same observation 12:23 made, that the prudent conceal knowledge while fools proclaim foolishness, and the repetition across chapters suggests the book found it worth saying twice. Nobody has to expose the fool. He handles it.
Related: Proverbs 12:23 · Proverbs 15:2 · Proverbs 17:28
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.