My building is well insulated against sound traveling between apartments. I once was able to hear some muffled music from up the hall, but it’s been otherwise silent (barring people actually hammering pictures up on the wall when they move in).

Sound from the hallway, though, permeates my front door like water through air. I’ve heard many cell phone conversations conducted there. I’ve heard the neighbors’ loud parties getting broken up (but not the parties themselves). I’ve possibly even heard the comings and goings of criminals back when there were criminals living across from me.

This is why it’s of some concern that my neighbors have not yet deciphered the great mysteries of the modern key.

Since they moved in I keep hearing knocking from across the hall, growing more and more intense over time, with added shouting and cursing occasionally. See, it seems the people who come most frequently to this apartment either do not carry or do not know how to use… keys.

So for anyone else out there who still has not mastered the concept, please understand: there exist bits of metal that are capable of opening locked doors. You can get them from your landlord, usually for no extra cost – they just come free right there with your lease.