Wooden Beam

A beam sits in the background and gives a torch something to hang on where nothing else will do. Stack them from the floor and they join into one unbroken column, so you can light an open cave or a mine shaft without laying wall or building a pillar of blocks that gets in your way. Where background wall already exists you can place them with nothing underneath.

They look like wall, but the game groups them with furniture. A tile holding a beam cannot also hold a table, a switch, a statue or a torch, and one placed beside a door will stop that door opening. That detail explains most of the confusion when a beam refuses to go where you want it.

Once torches learned to stick straight onto background wall, beams lost nearly all of their indoor purpose. Inside a finished house they are decoration. Out in caves and open shafts with no wall to attach to, they are still the tidiest way to light a vertical run. The Adamantite Beam and Palladium Column are not beams at all despite the names, they are ordinary blocks.