Legerdemain is the specialised hand that Dexterity is the general one: palming, cutting a purse, running a shell game, keeping four objects in the air. Dexterity covers what anyone might attempt — catching a thrown cup, grabbing a ledge on the way past it — while Legerdemain covers what has been practised until it looks like nothing at all.
The applications differ, but the training does not: someone who has drilled one of them acquires the others quickly, so the skill is assumed to cover any intricate or deceptive hand–eye manoeuvre a character cares to invent.
Sleight of hand — palming an object, lifting a purse — is an opposed test against the mark’s Awareness. Success at Legerdemain means the thing is done. A successful Awareness test at a higher success level than the thief’s, ties broken in the mark’s favour, means it was seen, whether or not it worked. Preparation can shift the odds: Stealth to come up unheard, Guile to hold the mark’s attention, each lending its Secondary Modifier to the attempt.
Entertainment — juggling for a crowd — is a Success Value test read as Dancing is, its Value Diamonds bearing on persuasion for as long as the audience is watching.
Elsewhere. Legerdemain substitutes for Dexterity in a Dexterity test and in its role as a Secondary Mastery, and twice its Index applies as a bonus to Throwing tests. It is also the skill a character keeps their grip with: a Fumble Test rolls the better of Dexterity or Legerdemain.