Spacing for anchors: Usable Length (in inches) / Total Length (in inches) * 12 inches. For my beds, I calculated a spacing of 11.75 inches for my 8 foot board by dividing the Usable Length of 94 inches by the Total Length of 96 inches and multiplying this by 12. My four foot boards require a spacing of 11.56 inches.
They are perfect for the disabled gardener, those suffering from arthritis, and the elderly as they can be elevated to a suitable level so that bending over and kneeling will not be necessary.
The close plant spacing and the use of compost generally result in higher yields with raised beds in comparison to conventional row gardening. Waist-high raised beds enable the elderly and physically disabled to grow vegetables without having to bend over to tend them.
I wish somebody would build a Square Foot Gardening grid that you can insert into a raised garden bed to mark off squares, but until this is available, if you want to use the Square Foot Gardening method, you will need to devise your own method for marking off squares.