Wood Platforms are thin blocks through which players can jump or drop (using the 'S' by default) through. They are often used to build bridges and ladders, or to cover pits since they allow passage in both directions.
Wood platforms can be attached to a background wall, a block, or another adjacent Wood Platform (including one directly above or below). They cannot be attached directly to the background of the dirt or stone underground layers, since the backdrops of these areas don't count as "walls". However the sections 'anchoring' the platform to a wall can be destroyed after it is built out, leaving floating platforms.
Lava will break platforms like a hammer on contact, unless they're protected with water. In this case, lava and water won't mix into obsidian, platforms will separate the layers (see picture below). This can be used to make traps for underwater creatures, like the shark trap.
Wood Platforms can be grappled onto, but they let projectiles like arrows and bombs through.
Players can use Wood Platforms to build an arena to effectively fight many bosses, as projectiles pass through them, striking the boss while offering plenty of vertical and horizontal space for the player to maneuver in.