You can pretty much use anything. We used 2-1x3's cut it to 64" tall (When cutting the bottom we cut it on a slant, so when we assembled it, it would stand flat.
We started from the bottom and measured 10" up and placed the 1x2 across the two 2x3's and then measured every inch and placed each board across.
There is a slant to the ladder, the bottom is 26" apart and the top is 16" apart. We used a brad nailer and nailed the boards. Notice all of the wood and saw dust, that was from cutting out the "family" blocks for our creativity day.
Puttied the holes . . .
and then sanded.
Now time to paint!
I didn't want it to look rustic at all, since it was going in Caitlynn's room. So once I painted, it was done and ready for quilts.