Al will know for sure but his posts look like the 1/4" diameter, 48" posts folks use to mark driveways for snowplowing. They have the reflective tape at the top which works great at night when trying to find your driveway in a snowstorm..
You can find 100 packs for about 75 cents a piece on ebay and if you get more than 100 they get cheaper yet. They come in blue, yellow, orange, green etc. I found my orange ones seemed to fade and deteriorate pretty quickly after a season in the sun. They also give nasty splinters when they split (fiberglass). I bought yellow ones for my driveway instead of orange this year just to see if they hold up better in the sun.
Usually they have a blunt bottom but the ones I got this year happened to have the bottoms tapered to a semi-point which helps me push them in by hand. I find they are very useful as a marker in the woods (the orange or yellow ones catch your eye from a distance) and are very helpful for putting up temporary fencing like above.
When they splinter (usually at the ground level from the snow pushing against them) I take a hacksaw to the splintered part and save the shorter ones for stakes in the garden when I plant my rows and before the seeds or tiny plants are easily visible.
very handy to have a few around. I store them in a section of 4" thin wall PVC cut at about 42" (with the bottom closed off with one of those caps that has the small holes in for drainage) that I had laying around as they don't tend to stay in one place when you try to stack 100 of them in the corner
I bet his idea will work fabulous for keeping the GBH out!
