How do I fix a warped kitchen cabinet?
I decided to try to install a cross brace inside the cabinet to spread the walls enough so the drawers would fit.

I made a trip to the hardware store and picked up:


A 1x6 pine board
Angle brackets with screws


Then I:


measured the front opening of the cabinet.
cut a piece off the pine board 2mm longer than the cabinet is wide.
used a rubber mallet to tap the board into place as a cross brace just underneath the top drawer.
tested the drawers to make sure they opened and closed with the cross brace in place
permanently attached the cross brace with the angle brackets.


It works perfectly.  I was prepared to add a second cross brace underneath the middle drawer, but all the drawers are working well without it.

Here is a picture of the repair with a red circle around the board that I added.