Recently, I picked up a gadget that is as useful today as when plows were wooden. It is a string line, and is a flat spool on a spike with a separate stake, connected by a line of string. The distance between the two is determined by how much of the line you unspool. If you grow vegetables, the device is transformative.
On a freshly prepared seedbed, the taut string forms a straight line. You follow it with your finger to make a little furrow into which you sprinkle your seeds. Move each end of the line the span of your hand for a new furrow, and you have perfect row spacing for veggies such as lettuce, beets and carrots. A line allows you to distinguish seedlings from emerging weeds, allows you to backfill rows with sand to avoid soil crusting, eases thinning and gives an order to the garden.