Wow...what a good bunch of ideas you all have provided:

- I never thought of the "loose board," "office staple" or "wooden
lath" solutions, so I'm going to try all of these and see which ones
work best in my particular situation.

Although the "wrapping the plastic around the carpet edges" won't work
on my wall-to-wall carpet [I forget to mention that that's the type of
carpet I have, which is not on a slab], it's a great idea that I can
try on the "non-wall-to-wall" carpet in another room.

Thanks, everybody, for your ideas!

Bob