Good morning,

I would like to ask some questions about non-subject relativization 
(construction of relative clauses referring to noun phrases which are not the 
subject of the verb inside the relative clause; they are, for instance, its 
object, instrument, place, etc.).

Just to clarify what I'm trying to say, a subject relativization would be, for 
English: "This is the man who sells hamburgers."
Here, "who", referring to "man", is the subject of the verb "sells".

Now, examples of NON-subject relativization in languages which use relative 
English: "This is the knife 'with which' I cut the bread."
Portuguese: "Essa  a faca 'com a qual' eu cortei o po."
Here, "with which"/"com a qual", referring to "knife"/"faca", is the instrument of 
the verb "cut"/"cortei", and not its subject.
The examples above use the relative pronoun "which"/"a qual" with the 
preposition "with"/"com".
In languages with declension, this pronoun would assume a declined form.
For example, Sanskrit (in ITRANS transliteration scheme, without sandhi):
yena astram shatrUn hanmi etad asti.
"This is the weapon (etad asti astram) with which (yena) I kill the enemies 
(shatrUn hanmi)".
Here "yena" is the Instrumental case of the relative pronoun, rendering the 
meaning of the preposition "with".

My questions are:
- What are other possible strategies for non-subject relativization?
- The examples I gave above are for nominative-accusative languages. How 
would an ergative-absolutive language, for example, render this situation?

Thank you in advance.