The theory of language structure informs us about what we should expect when we want to investigate a certain construction. However, reality is often richer than what theories predict. In this study, we start from a theoretically informed set of hypotheses about the structure of wh-questions in sign language, we test them using a sign language corpus, a designed production experiment, and structured fieldwork in three sign languages, Swedish, Greek and French Sign Languages. The results will inform us on what type of contribution each research method can provide to reach accurate language descriptions.