generated at
make certain

with clause take action to ensure that something happens or is the case:
«…を/…だと/…かを» 確かめる(make sure) «of/that節/wh節・句»
e.g. I made certain that our paths would never cross again.
establish whether something is definitely correct or true:
«…を/…ということを» 確実にする, 確実に手配する(make sure) «of/that節» (!that節中は未来形にしない)
e.g. he probably knew her, but it didn't do any harm to make certain.