While I have a decent sized kitchen, one thing I've always missed is a cabinet for cutting boards and cookie sheets. Sometimes in a kitchen there is one tall, thin cabinet with vertical dividers so you can store long items in it, but mine did not have it. So, I decided to put in my own. First I cut out the existing shelf.
Then I made tracks for the vertical panels at the top. The tracks were made out of 2x3's mounted across the cabinet, just below the drawer. Using my circular saw and working 1/8" at a time, I cut out 3/8" wide 3/4" deep grooves into the 2x3's (this would have been MUCH easier if I had a router). These were then screwed in and the vertical panels installed.