Lingopro Nov 30, 2014:

I'd say "bridging pieces" - or pieces for bridging the gap between...
Sorry, I don't see what else it could be. It's just a piece of drywall, cut to size to fill the gap.

Daniel Rabinovich (asker) Nov 30, 2014:

Thanks, Lingopro, maybe I closed the question too fast.
In any case your suggestion, like Simon's, does not reflect the exact situation that is described in my original document - two levels of ceiling, where the "megasher" closes the vertical gap between them.

I think the vertical surfaces shown in the pictures on this page are what is meant:
http://www.lemurzone.com/rfg/index.php/category/cornerbead/

Lingopro Nov 29, 2014:

Daniel, look at this link, on page 2, under "Studs", it says "mid-height bridging" (I couldn't search the page), so maybe you can work with that. Have you found out what the bridging "agent" is?

http://www.e-ztape.com/tech/pdf/wall_assemblies.pdf

Daniel Rabinovich (asker) Nov 29, 2014:

I am aware, but the relevant Israeli standards use "Gypsum", therefore so did I.

Simon Charass Nov 28, 2014:

@ Daniel In North America the term used is "drywall" not gypsum. It depend on the target country.

Simon Charass Nov 27, 2014:

The link I posted http://homeguides.sfgate.com/fix-uneven-joists-before-drywal... deals exactly with the drywall/gypsum panels.

Daniel Rabinovich (asker) Nov 27, 2014:

These are gypsum ceilings wer'e talking about, they're not supporting structures. I think these elements are added just so that a hole is not left between the two levels.

Lingopro Nov 27, 2014:

Why not support beams?

meirs Nov 26, 2014:

מדוע הם חוזרים על מה שברור מאליו הכל יבוצע כנדרש במסמכי החוזה - בשביל זה קיימים מסמכי החוזה