The dummy is me. 
I live in a terraced house which has a fenced backyard, front half of which is flagstone patio and the back half is lawn. I would like to create a strip of garden along one side of the lawn, ie going from the edge of the patio to the end of the property. It gets pretty much all day sun, so think stuff would grow.
So far I have dug up the grass, but there’s no real differentiation between lawn and dirt, so it doesn’t look very nice.
What is the simplest, laziest, way for me to differentiate the lawn bit from the garden bit? Can I grab a plank of wood, stick it sideways into the ground and declare the dirt side of it a garden? Or do I need to do something more robust?
For simple and lazy, a board would work, although you want to use something like cedar or pressure-treated* so that it isn’t rotted out by next year. You can also buy plastic edging that goes in the ground that does not make much of a visual impact but can be mown over rather than requiring separate edging.
Personally, I would look for some kind of stones or bricks that would compliment the patio. Stones or bricks are obviosuly heavier than wood though, so this does add the complication of getting them to your home if a substantial amount is needed.
You definitely want something though because besides looking nicer it keeps the grass from growing back into the garden beds.
*There is some question on whether you really want to use pressure-treated in the garden, especially if you are growing vegetables, but I am not really sure how worrisome it really is.
I’ve used patio pavers (similar to bricks) to edge gardens. You can just lay them down in a row. It’s good to put some weed-blocker under them, but you can use folded newspaper for that. Wet it a little to get it to “stick.” They’re also easy to rearrange or re-use.
And here’s my #1 tip for new gardeners–choose plants that are native to or naturally thrive in your area. Then you won’t have to do fancy mumbo-jumbo to keep them alive. (And I include daily watering in “fancy mumbo-jumbo.”)
Thanks for your responses. I’m thinking some sort of brick may be the way to go, and will match with the brick of the terrace.
The classic, cheapest, and probably easiest way to do it is to just edge it with a shovel like shown here. I worked as a landscaper for a few years, and we always just used a straight edged shovel to do it.
Missed the edit window - I found a good video!
They stopped selling the arsenic treated stuff in 2003; as long as you’re using wood that was sold after that, you should be fine. link.
I like a block that can give you 8 inches of width between the grass and garden. You can run the mower wheel on the block and not deal with tedious grass trimming.