A movable windowsill

Though my house has south-facing windows with plenty of light for starting new plants, the windowsills are too narrow to hold a flat of seedlings or the trays of cuttings I root each year. To make convenient shelves for the plants, I bought several inexpensive, height-adjustable ironing boards. They take up very little room, and can be wiped up easily if I spill when watering. I can raise them to windowsill height and set them right against the sill so my plants get all the sun they need.