hi,
I'm in the process of renovating the lawn in my backward and while I was digging up dead weeds and grass as a preparation, I found a green nylon net laid out underneath the lawn. I think the previous owner or whoever did the lawn last time placed it under the lawn, but I wonder what it is for. Is it common to place a net under the lawn and if so, what is it for ?
I'm looking for the answer for this question to figure out whether I should do the same.

Thanks