I faced the task of putting two shelves into a big old beautiful wooden cupboard.
The wood of the old cupboard is not totally straight, it is brittle and somewhat sensitive to forces and one would not want to really rely on screws or nails to hold shelves on its rather thin side walls.
So I came up with a solution and here is what I did.
The overview shows the cupboard, open doors. I put in two boards to put stuff in.
In each corner of the cupboard, I placed a rectangular bar made of really dense hard wood. These were not really cheap.
The photo series shows the left bar in the back of the cupboard, from top down, in close up shots.
For the shelves, I used precut boards that roughly matched the size. Then I cut them lengthwise to be a bit less deep and I elongated their width as you can see. Then I also cut out rectangular bits for the bars. This images shows the upper shelf.
Each bar was supplemented with a bit of the left overs of that hard wood. I used metal strips and long wood screws to fix these bits into place. I did that from both sides.
The lower shelf has the same setup.
As you can see I just used the cut off bits of the bars to act as shelf holders. Same expensive hard wood I guessed they’d do the trick.
The bars are just standing on the lowest board, under which the cupboard has its pedicles.