When we moved into this (ancient) house almost twenty years ago, a single page of instructions was left for us. Particular attention was called to the many hagstones around the place, and that they ought to stay with the house, with a definite implication of ‘or else’. My inclination has always been to add to the collection, plus I’ve gone on to make plenty in #glass They are also called Holy Stones - or Holey Stones :) and only good
things are supposed to be able to pass through the hole. Apparently you can also use them to see through a witch or fairy disguise - but it seems a rather obvious way of showing you suspect a body, and might give offence either way.