How to draw 2d above 3d scene?

I have an OpenGL(3.3)+GLEW application. I want to draw a black vertical rectangle at the left side of the window for writing some information on it, like fps (I use GLEW function for drawing text).

I have a common pipeline, like this:

 m_transformation = PersProjTrans * CameraRotateTrans *
CameraTranslationTrans * TranslationTrans *
RotateTrans * ScaleTrans;


I know how it works, but I can't figure out how to draw a projection of the rectangle on the window, like 2d.

I should also note that to overlay 2D over 3D, you'll have to disable depth testing before drawing the 2D parts. I.e.: glDisable(GL_DEPTH_TEST);.