Как сказать "settings", or "set format"?
Kamillion -- note that the word "set" in set format can be understood as either a verb (in which case the meaning is something like "choose a format from a list of options and save your choice") or an adjective (in which case it means something like "a fixed/established/pre-determined format").

Regarding сотрудник, from an etymological standpoint it definitely means "co-worker", and can sometimes be translated that way. But in many contexts, "employee" is actually a better translation, and is sometimes the only possible translation. For example, you can say in mixed English/Russian: "Jane Smith, a stay-at-home mom, claims she was harassed by a сотрудник of the FBI." In that case, сотрудник cannot be a "co-worker" (of Mrs. Smith), but can only be an "employee" (of the FBI), because a "stay-at-home mom", by definition, does not have co-workers!

As far as tool rentals go, I think it'd be generally correct to say брать/взять (какой-нибудь инструмент) followed by на прокат or внаём or в аренду. (But note that rentals of real estate, as opposed to tools or cars or bowling shoes or hookers, would generally use a different verb construction.)

From Googling, for example, I found this site for people who need to rent power construction tools in Yekaterinburg -- the headline says ИНСТРУМЕНТЫ В АРЕНДУ - НЕДОРОГО И УДОБНО ("Tools for rental -- inexpensive and convenient"). And the rhyming slogan at the top left says Прокат без преград ("Rental without obstacles").

And also from Google, арендатор seems to be the appropriate word for a person who rents a tool from someone else. (Заемщик, from what I can tell, is used primarily in the context of borrowing money, and according to some online sources, it's somewhat old-fashioned.)

But I'm not a native speaker, so I would definitely get a second opinion!