How to make a background for health bar?

Hello, I want to make an health bar, but i have a problem. I made two bars : red and grey. The grey one should be under the red (as a background), but I don’t know how to do it. When I’m adding them to game, the grey is above the red bar. Both of them are made in Gimp.

Place the red bar as bottom as possible in the Hierarchy. And make sure that the Z position of the red bar is in front of the gray bar.