Harry put the watch glass, compass and pendulum down, and dabbed a bit of the blood with a cue tip on the latter two objects. He then chalked a circle around the objects, and with a bit of will, closed the circle and started casting the spell to create the connections between the blood and the people bearing it -- Edward and William excepted -- and to make the compass and pendulum respond to that instead of what they normally did.
It didn't look like much; there wasn't even a flash of light like you got with alchemy.