Abstract: In 2019, Budney and Gabai introduced a concrete way to construct diffeomorphisms of 4-manifolds called barbell diffeomorphisms. We will review this construction and use barbells to construct interesting knotting in S^4 and S^5, including knotted splitting spheres and knotted solid tori in S^4, and knotted 3-spheres in S^5. This is partially joint work with Seungwon Kim and Gheehyun Nahm.