What good is half a wing?
The question "what good is half a wing" is often used by creationists who severely misunderstand evolutionary theory. The question relates to the idea that fossil birds should be discovered with literal "half-wings", i.e. a wing missing half of itself. This is a misunderstanding of how wings evolve. Evolution has no goal, so it's not working towards a full-blown modern wing like we know them today. All it's doing is working towards something that helps the organism in some way. For example, a dinosaur's arm could grow small proto-feathers in order to help it stay in the air longer when it jumps. This isn't a wing yet, but it is beneficial. Over the millenia, the feathers grow, the arms and muscles change, and by modern times we do have wings as we know them.
This argument is related to the idea that evolution is like a tornado moving through a junkyard and assembling a fully-functional 747.