Complex sentence: Whatever its name, the crossing remains relevant, as Gibraltar opted out of the European Union Customs Union and is not part of the Schengen area; it is open 24 hours a day with customs duties payable on certain goods entering Spain or Gibraltar.
Split into simpler sentences: Whatever its name, the crossing remains relevant, as Gibraltar opted out of the European Union Customs Union and is not part of the Schengen area. The crossing is open 24 hours a day with customs duties payable on certain goods entering Spain or Gibraltar.