But it is useful.
There is a community garden project in Milwaukee that is pretty darn cool; Every spring, people can sign up for a little garden plot.
src: victorygardenmke
Those plots need to be numbered. Not something too permanent, but it has to be durable. It needs to handle the weather outside for the spring and summer.
I make laminated cards for this. But it's not quite as easy as it sounds- if you just laminate a page and cut out the numbers, water can get right in through the sides of the laminated card. The trick is to have a laminate border around the card.
Then we use a good thick outdoor double sided tape.
If you live in downtown MKE, you might have seen these garden plots around local parks.