The same manual markers used in the antecedent of factual, counterfactual, and concessive conditional clauses may be optionally employed to mark the antecedent of non-predictive/peripheral conditional clauses.
In the presence of the optional manual marker, the obligatory non-manuals marking the antecedent clause are also produced. When the manual marker is absent, the obligatory non-manual markers alone are able to mark the sentence as a conditional clause.