Spell Mechanics

[Amy Z]

No: HPFGUIDX 24495

Robyn wrote:

> What are some of the mechanics of spell casting in the Potterverse? 
> The Summoning Charm, for example - is it limited to line-of-sight? 

Definitely not.  Harry's worried he won't be able to Summon the 
Firebolt because it'll be so far away, and Hermione says it makes no 
difference--and she's right.  They even contemplate Summoning an 
aqualung for task #2, but decide it would attract too much Muggle 
attention.  I love the image of scuba equipment soaring over hill and 
dale.

I wonder about locks and such.  Harry wishes for his knife when he's 
underwater, but it was "locked in his trunk in the castle a quarter of 
a mile away, no use to him whatsoever" (GoF 26).  Is this a case of 
his forgetting his newly-learned charm, the way he does in the 
previous chapter (when he could have saved himself a lot of trouble, 
and incidentally short-circuited the entire plot, by Summoning the 
map)?  Or, and this is what I reckon, is it impossible to Summon it 
because it's locked up?  He'd need to add unlocking charms.

Closed doors, I'm confident, don't stop a Summoned object.  The 
Firebolt probably had to get through several:  definitely the portrait 
hole and the front door, probably the dorm door as well.  I wonder if 
the doors swing open and shut again, or does the object just sail 
right through them . . . ?

Amy Z

Maple, unicorn hair, 9 inches 
according to Joywitch Ollivander Curmudgeon