In article , Nospam@invalid
says...

If your purpose is simply to prevent weeds, at preferably no cost,
then you might try a visit to your local council tip and have a word
with the people there about the possibility of removing an amount of
carpitus oldicus which someone else has deposited there. This will be
more resilient than uncovered cardboard.

If you do, be sure to get canvas backed, preferably something slowly
biodegradable like wool or sisal.

Foam or rubber backed nylon disintegrates very messily into a zillion non
biodegradable bits.When I need some old carpet I just ask the local
carpet fitter and he drops some off free; it saves him money because he
has to pay for disposal of old carpet he removes before fitting new. I
don't use carpet on edible crop beds; they may leach all kind of chemicals
from dyes etc into the soil. Useful for paths though.

Janet