A Mom with Nails: {How to make} Adjustable Shelving

I float from project to project, depending on my mood, where C wants me in the house and other rapid day to day changes. This afternoon, we ended up upstairs, and while I listened to music he picked to play on the computer (which is very familiar if you were a child of the 80's), I went to work on my office shelves again. To make an adjustable shelf, I used two techniques I've learned over the years. The first was from a handyman we hired to build a huge built-in in our living room; the other? I have no idea. Probably dates back to some show on TV, but I don't remember. But here goes:

The first thing I did was pick out a drill bit size that would fit the adjustable pegs that came with this shelf. This was was a little snug, but I thought it would work better than the one that was a tad loose.

This is a scrap piece of lumber that I used to ensure the holes would be the at the exact place on each side of the boards. I drilled three holes in it, and used it as my template four times. I sat the board against the bottom of the shelf each time, tried to keep it plumb (level on a vertical), and re-drilled each time through the same holes. (Thanks handyman....I've waited years to be able to use this tip!)

To know how deep to drill, I sat the drill in the hole (both through the template and through the depth of the actual hole. Then I placed the tape at the depth I needed. When the drill went in up to the tape, I was done. Worked like a charm! Depth is important here: If I drill too deeply, the hole is going all the way through, and I will see the hole on the other side of the shelf. Don't want that to happen!

This is one side of the vertical piece (which used to be a horizontal shelf...confused yet?) with the newly drilled holes on one side. Don't they look nice and even?