I have a 2x4 wood rail between two 4x4 wood columns. It looks something like the drawing below:
The 2x4 rail is warping a little bit, so I want to attach a 2x4 under it so that it can straighten the rail. But I don't want to use screws that will be seen from the top of the rail.
What can I do to securely attach a 2x4 under the 2x4 rail without having to drill at the top of the rail? Or is there a better way to straighten the 2x4 rail?