Most products stay in place through a snug stretch fit over the arm. You can also use discreet Velcro strips on the underside edges to adhere the cap to the frame firmly. Attach a self-adhesive gripper shelf liner to the arm edges for a no-slip fit before slipping on the cover. Avoid visible staples, nails, or tape that could damage the arm finish. If caps are loose, carefully hand-stitch fabric darts or pleats to remove excess fabric and tailor the fit.