diff --git a/src/block/Block.php b/src/block/Block.php
index b2847bb35..d6158ea94 100644
--- a/src/block/Block.php
+++ b/src/block/Block.php
@@ -576,6 +576,15 @@ class Block{
 		return false;
 	}
 
+	/**
+	 * @deprecated TL;DR: Don't use this function. Its results are confusing and inconsistent.
+	 *
+	 * No one is sure what the meaning of this property actually is. It's borrowed from Minecraft Java Edition, and is
+	 * used by various blocks for support checks.
+	 *
+	 * Things like signs and banners are considered "solid" despite having no collision box, and things like skulls and
+	 * flower pots are considered non-solid despite obviously being "solid" in the conventional, real-world sense.
+	 */
 	public function isSolid() : bool{
 		return true;
 	}