The situation
Hiding places do not travel.
Most people's home copy of anything important is somewhere specific: a drawer, a book, a box at the back of a wardrobe. That logic dissolves the moment the contents of a flat are anonymous cardboard.
Moves are also when things vanish. Not stolen, misplaced, given away, left in the loft for the next owner.
The advantage of holding three cards is that a move only puts one of them at risk at a time.
Before the van
A short moving protocol.
-
I
Carry one
The card that normally lives at home travels on you, in a wallet, not in a box.
-
II
Leave one
Keep a copy somewhere that is not moving: a bank box, a relative, an office drawer.
-
III
Never label
Do not write anything on the card or its sleeve to help you find it later. That note helps everyone else too.
-
IV
Re-place it after
Once you have unpacked, choose the new hiding place deliberately instead of leaving the card wherever it landed.
Three cards
means one can be in a box.