There is no specific manual marker that encodes temporal simultaneity. Temporal simultaneity between two events is expressed by non-manual markers. One of these non-manual markers is head thrust which is used to mark other types of adverbial clauses, as well.
h-th
[frıend home come] ıx1 holıday plan
‘When my friend came home, I was planning the holiday.’
Anteriority of an event with respect to another event is expressed by placing the subordinate clause denoting anteriority before the main clause. The subordinate clause contains a manual sign after. The syntactic position for this manual sign is the right edge of the subordinate clause:
h-th
re
[poss1 frıend home come after] holıday plan
‘After my friend came home, I planned the holiday.’
Before-clauses usually have the negative marker not even though the event in the subordinate clause is not semantically negated. The syntactic position for this manual sign is the right edge of the subordinate clause, right after negation:
h-th
re
[frıend home come neg before] ıx1 holıday plan
‘Before my friend came home, I planned the holiday.’