Like many caravan cupboards, mine had space for an extra shelf but without one being fitted. I used some pieces of Formica which I had to hand in the workshop. First, a piece was cut just slightly smaller than the shape of the cupboard.

Then edging was cut from 12x12mm square timber and glued on the underside of the Formica. To support the shelves I fixed four equal lengths of 6mm dowel rods in each corner lightly held in place with a single dab of glue. The shelf sits on the four dowels. If at some time in the future the shelves need to be removed, they can be quickly dismantled.