Not an eBay interaction but, a face to face when I was with a company making and selling bricks and pavers.

Chap ordered required quantity of pavers and also requested "......that stuff you use to stick them down".

Brief explanation of the installation process later, he said he knew all that but, still needed the stuff to kep them down.

"Yellow sand?"

"No, the stuff that keeps them in place"

"Jointing sand?"

"No, no!  The stuff that stops them from lifting off"

"Ummmmmmmmm....................gravity?"

"Yeah!  Where can I get that?"

Absolutely true as I sit here.