Knock spell versus Arcane Lock

[RobRendell]

Hi! I searched and didn't find anything that directly helped resolve my confusion about the interaction between the spells Knock and Arcane Lock.

Here's the text of both spells:

Knock:

Knock opens stuck, barred, or locked doors, as well as those subject to hold portal or arcane lock. When you complete the casting of this spell, make a caster level check against the DC of the lock with a +10 bonus. If successful, knock opens up to two means of closure. This spell opens secret doors, as well as locked or trick-opening boxes or chests. It also loosens welds, shackles, or chains (provided they serve to hold something shut). If used to open an arcane locked door, the spell does not remove the arcane lock but simply suspends its functioning for 10 minutes. In all other cases, the door does not relock itself or become stuck again on its own. Knock does not raise barred gates or similar impediments (such as a portcullis), nor does it affect ropes, vines, and the like. The effect is limited by the area. Each casting can undo as many as two means of preventing access.

Arcane Lock:

An arcane lock spell cast upon a door, chest, or portal magically locks it. You can freely pass your own arcane lock without affecting it. If the locked object has a lock, the DC to open that lock increases by 10 while it remains attached to the object. If the object does not have a lock, this spell creates one that can only be opened with a DC 20 Disable Device skill check. A door or object secured with this spell can be opened only by breaking in or with a successful dispel magic or knock spell. Add 10 to the normal DC to break open a door or portal affected by this spell. A knock spell does not remove an arcane lock; it only suppresses the effect for 10 minutes.

Say we have a door that has a superior lock (Disable Device DC 40) which has also been Arcane Locked (raising the Disable Device DC to 50).

Which of the following happens when a Knock spell is cast on the door?

• The caster of Knock makes a caster level check + 10 against the augmented DC of 50. If successful, the door unlocks and the Arcane Lock is suppressed for 10 minutes, after which time the door locks again.
  
• The caster of Knock makes a caster level check + 10 against a DC of 40 ("against the DC of the lock"). If successful, the door unlocks and the Arcane Lock is suppressed for 10 minutes, after which time the door locks again.
  
• The Knock spell automatically suppresses the Arcane Lock spell for 10 minutes ("If used to open an arcane locked door, the spell does not remove the arcane lock but simply suspends its functioning for 10 minutes"), but the door remains locked. For the next 10 minutes, the door can be unlocked with Disable Device or another casting of Knock against a DC of 40.
  
• Something else...
  

If the correct ruling is the first, it seems that even a 20th level caster isn't likely to unlock that door. He'd be better of casting Dispel Magic on the lock to dispel the Arcane Lock first (caster check vs. Arcane Lock caster's level + 11) and then casting Knock.

[Thanis Kartaleon]

I would say the second ruling is correct. The arcane lock is suspended, and then you make a caster level check against the DC of the lock with a +10 bonus.

[Skylancer4]

I would also say the second ruling would be the correct one assuming there is only a single lock. "Two means of closure" would be (1) disrupting the Arcane Lock and then (2) functioning on the existing lock.

If there were two locks you would end up neededing a second spell if one were Arcane Locked due to the limit it would seem.

[RobRendell]

Ok, that makes sense - one "means of closure" is the Arcane Lock, which is automatically suspended, and then the caster's roll is compared against a second "means of closure" without the benefit of the Arcane Lock. If the roll succeeds and that's all the things fastening the door dealt with, the door is unlocked (until the Arcane Lock resumes in 10 minutes). If the roll fails or there are more fastenings, subsequent Disable Device checks or more Knock-ing is required (with a 10-minute window with no Arcane Lock).

Presumably in a different situation, where a door with no regular mechanical lock has been Arcane Lock-ed (creating something that would require a DC 20 Disable Device check to open), the Knock spell would automatically suspend the Arcane Lock and the door would unlock without requiring a roll at all.

Thank you both!