To accomodate all of the bathroom 'essential stuff' my DW and I feel the need to bring along, I installed extra shelves in the bathroom medicine and small corner storage cabinets.
The shelves are made from thin (about 1/4") laminate flooring approxinately the same color as the cabinets. I ripped the tongue off but left the groove sice it was flush to the edge. The front edging was made from innexpensive 3/4inch 'plastic'
corner moulding, raising the edge so when the door is opened at the end of our journey we don't have things tumbling out. The rear and the end supports (visable in the medicine cabinet picture) are again cut from 'plastic' 3/4inch
cove moulding. I used small screws to hold the supports in place until the glue dried. All of the materials were purchased at Home Depot for less than $20.00.
I'm not a cabinet maker
so they're not exactly "cabinet grade" but they do serve the purpose very nicely.
Kevin