Rules about when to use "tegoż" in sentences

Hi everyone! :)

This is just a quick question. For awhile now, I noticed the ocassional use of the word tegoż used in certain text, such as "osób używających tegoż narzędzia." I was wondering when it should be used as far as grammatical rules are concerned, since I would probably have (guessing incorrectly) used "te narzędzia" in the example before. Any ideas? :)

Dziękuję! :D

No. Correct would be "tego narzędzia" or "tych narzędzi" If narzędzia are plural.

You may use tegoż instead of tego... not even sure If there are some formal rules...

You replace "tego" with "tegoż" if you want to sound smarter or more formal ;-) But it comes out pretentious.

But sometimes it's a more emphatic form which means something "this one, not any other".

The -ż is an emphatic particle which as the name implies streses the word it is tacked onto. For instance co is what but cóż could mean what in tarnation as in:

Cóż on najlepszego powyczyniał.
Gdzie byłeś? (where were you?) is rather vapid, but Gdzieżeś był = where on earth have you been? For added emphasis add on: do jasnej cholery.

Tego narzędzioa is this tool but tegoż narzędzia might mean this very tool, showing how different langauegs use different devices to relay a similar message.