Exactly what it says.
Say you have a locked door. Can you nest multiple layers of arcane lock onto that the same door?
If so, would you need multiple Knock spells or Dispel magics to overcome that configuration?
Sort of thinking along the lines of:
Group X wants to seal away a non-aging monster and wants to make sure the door can't be opened by anyone but them.
They cast several arcane locks, each with their own password.
Much later, evil bad guys minions go on a quest to recover each of the passwords.
Obviously this would be a fairly low-level lot since dispel magic would work just fine, but for an example, it works fine.
Secondary question; can you nest multiple magic traps onto the same door? Like if the evil bad guys try and force open or pick the arcane locked door;
could multiple magic traps go off at once on the poor failing rogue?