How to render one line on top of another without flickering?

This is probably a really simple question, but I'm trying to understand what's the best way to render one line on top of another (e.g. for a health bar) that are on the same z-plane (in a 3D game).  I have two GameObjects, one called Gauge, which should be rendered on top of GaugeBackground.

I would have expected that by setting the depth offset factor to -1 for Gauge, it would always render on top of the GaugeBackground.  However, instead, it flickers.  This is true even if I set the depth offset factor to 0.  I have tried setting the Depth Test to Always, and that does make Gauge render on top of GaugeBackground without flickering, but this seems a bit hacky?  I'm trying to understand what's the right way to do this.  See below for how Gauge and GaugeBackground are set up.