Why do GL lines not show in build mode

Hello -

I have a script that draws a bounding box using GL. This works fine in the editor, but when I build the app, I am not seeing the lines. I draw the lines in OnPostRender() using code like this:

void OnPostRender()
{
	GL.Begin(GL.LINES);
	material.SetPass(0);
	GL.Color(Color.white);
	GL.Vertex(...);
	GL.Vertex(...);
	...
	GL.End();
}

Can anybody tell me what I seem to be overlooking?
Thanks very much.

Hello again -

Found the answer thanks to a helpful blog:

https://forum.unity.com/threads/lines-shows-in-editor-mode-but-not-when-game-is-running.335981/

The script needs to be attached to the camera. I wasn’t doing that.

Oh, well … Live and learn!

Thanks.