Jtshy Jumbo Silver Jingle Bells,(24 pieces)

Q: How many, how much and how big?

There is 24 bells. They are slightly larger than a large grape. I put two of these bells on my dog's collar and know where he is on my property. Works well.

Q: Can they be heard if hung from a door knob.?

They need a good shake for that to happen, so just opening a door, not likely. Perhaps if there were a few tied together.

Q: I need bells for my fence so my puppy won't climb the fence. Loud, too. Maybe string them?

Loud, they are not. And they rattle more than ring. Had the same idea of stringing together and hanging on a fence as a sort of alarm when the gate was opened. They might let you know the puppy was at the fence but I don't see them being noisy enough to scare the puppy back.