A good balance starts with the frame—think aluminum alloy or carbon‑fiber composite for weight and impact resistance. Inside, use precision‑machined inserts that lock the parts into place; that gives you the “snaps” you want without sacrificing alignment. Keep the modular joints on a single, well‑toleranced surface so the parts don’t shift when the case is dropped. The trick is to design the snap‑mechanism to use a small, strong pin or a magnetic catch that can handle a few bumps but still be easy to assemble. That way you get a rugged case that still feels exact when you pull out a screw or a tool.