Minecraft wiki entry for Chest, associated text: A chest placed adjacent to another chest joins to create a large chest (also known as a double chest). A player can prevent this, and place two small chests side by side, by sneaking while placing the second chest‌[JE only], pushing a chest into place with a piston‌[BE only], or placing the second chest facing a different direction from the first chest. Alternatively, trapped chests do not combine with normal chests.