Although, no relative pronoun in a strict sense can be found in LIS, a sign is typically used to mark relative clauses. It is traditionally glossed pe.
pe
This sign functions as a determiner (LEXICON 3.6.1). pe can appear in restrictive relative clauses (SYNTAX 3.4.2.1) to univocally mark the referent that the relative clause predicate something about. In this syntactic construction, pe agrees with the head of the relative construction by being produced in the locus in space associated with it.