SSP BLKHD UNION W/LOCKNUT

That's exactly what this fitting is built for. The locknut that comes with it pulls the fitting snug against the panel or wall surface and holds it there so the line doesn't shift or work loose under normal operating conditions. It gives you a fixed, stable connection point right through the mounting surface, which is what you need when you can't have a line flopping around or pulling away from the bulkhead.