Minecraft wiki entry for Trapdoor, associated text: Trapdoors can act as a solid block when in the closed position and thus certain items can be placed above or below it. When trapdoors are opened, they act like a non-solid block resulting as a non-placeable area. Lanterns, for example, can be placed on top and below the closed trapdoor‌[Java Edition only]. In Bedrock Edition, lanterns can't be placed either under or on top of trapdoors. This could potentially be known as a bug or the functionality of placing lanterns under trapdoors aren't available as part of the game yet. The same goes for other decorative blocks (flowerpots, torches, and etc.).