I'm looking for the name of a specific Belgian WWII anti-tank obstacle or tank trap. I've been completely unable to find a name for it, or photos, or even other descriptions that match.

In 1988, I interviewed my grandfather, who was 78 at the time, tape recording his experiences in WWII escaping Belgium and joining the French Resistance. He was a mechanical engineer (who was in fact, still working as an independent contractor at the time I recorded him - still had all his wits about him) so I think his being mistaken - while not impossible, is unlikely. I'm also wondering if they were used for some OTHER purpose than as a tank trap?

So, hoping to find out what this thing is called, and if it's not a tank trap, then what was it?

Anyway, here is his description:

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"Before the invasion of Belgium, we worked in manufacturing something the Belgians were very proud of, some sort of huge cylinders maybe diameter of 5-6 feet by 8 feet long. Heavy cylinders, made out of I forgot what, concrete and metal, and those cylinders were--many thousands of them--interconnected by very heavy chains, a link having two feet long.

Over the entirety of Belgium there were lines like this, and they were supposed to stop the German tanks because a tank will push the cylinder with the chains dragging, and it would behave like a like a spider web, and the tank would be entangled in it, and couldn’t get out.

Well it looked very attractive, but Belgium was neutral, and therefore didn’t keep anything secret. They showed it to everyone who wanted to see it. And the Germans knew sufficiently about it and built tanks which had cranes on them and those cranes lifted the cylinders and shook them like that, breaking the chains, and everything was completely useless.”

Finally - my apologies for the empty post last night - I had a glitch on my phone when posting, so I deleted it.