I made this garden bed so it could be moved. This idea is that I can plant my perennials such as daffodils etc. in it and let it sit out of sight most of the year. Because it is easily moved I can then fetch it out to the side of the driveway when the flowers are in bloom. Because the size isn't a consideration the only thing that I really cared about was minimisation of waste and that is how I decided on this 2100 or 7 foot long bed size.