These unusual Labrico objects hail from Japan.

Slide these onto the end of a piece of lumber, slightly shorter than your room. Screw an upside-down leveler until it touches the ceiling, securing the makeshift post. A cap on the bottom protects the floor.

While not meant for structural support, it should securely hold the wood in place. In Japan, a similar ceiling-contacting mechanism is used to prevent bookshelves from toppling during earthquakes.