Today we have ‘keyless’ cars and access by touchpad or other electronic devices.  Passwords are essential keys to computer files and something to be guarded with great care.  In ancient times keys were much simpler and also much larger!  The basic principles of the pin tumbler lock may date as far back as 2000 BC in Egypt; the lock consisted of a wooden post affixed to the door, and a horizontal bolt that slid into the post. The bolt had vertical openings into which fitted a set of pins. These could be lifted, using a key, to a sufficient height to allow the bolt to move and unlock the door.  Such keys were large and worn slung over the shoulder.  Shebna and Eliakim were in effect the Prime Minister, able to act in the King’s name.  The disciples would immediately have understood what Our Lord meant by entrusting St Peter with the keys of the Kingdom of Heaven.  This is why the role of the successor of St Peter is not simply a human organizational structure but part of our faith as Catholics.  Part of Our Lord’s plan for his Church was that there should be a human person entrusted with authority on earth to make final decisions in matters of teaching and discipline.