-wood for shelves (I used 1/4" thick red oak planks, backed with 1/4 - 1/2" thick red oak for support)
-wood for cross bars (I used 1/2"x1.5" red oak)
-shelf brackets (< 1.5", to support cross bars, need 8)
-shelf braces (look for 'mending plates' - straight brackets to support cross bars, need 8)
-wood finish (I used 50/50 tung oil/mineral spirits)
-1/2" - 5/8" wood screws
Not having a table saw or planer, I used craft wood that has already been (mostly) squared and nicely planed. I chose oak. This project could be built for much less $$ if you have the ability to cut and plane your own boards!
Step 1: Prepare the ladder
Step 2: Add the braces
The straight braces are screwed to the underside of the ladder steps. You might notice that when the ladder is oriented so that the back rails are perpendicular to the floor, the steps are slightly slanted. In order for the wooden shelves to be level, the metal braces need to be bent until they are level.
The square brackets are screwed to the inside of the back rails. The cross braces will be screwed into both sets of brackets.