Methods generating fusion proteins with rigid and predictable structures have been developed in recent years. Among them, helix fusion methods that link two proteins by connecting their terminal alpha helices into a single and extended alpha helix can be particularly useful because designing fusion helices is conceptually and technically simple. These methods have been shown crucial in obtaining crystals that diffract x-rays to high resolution or attaching large and symmetrical backbone proteins to small target proteins for cryo-EM analysis. The structural rigidity of the fusion helix is crucial for these applications, and the reduction of structural ambiguity and flexibility at the fusion sites will further enhance the usefulness of this method.