Card maker,
What thickness would you recommend? I assume soft steel is best.
Les

From my link posted?
Feeler gauge stock from 0.03 up to 0.05 mm; my Shimmed Card Deluxe Strong is 0.05mm.
Feeler gauge stock does stay flat under all conditions!

Magnet - an object that attracts ferromagnetic objects
Ferromagnetic - an object that it's the property of being attracted to a magnet.
Magnetic - short term for ferromagnetic
Magnetize (verb) - the act of turning a ferromagnetic object into a permanent magnet
Chopped - an object that has a permanent magnet secretly inserted in order to facilitate magic effects (my words)

There is no dictionary term for an object containing a magnet.

Does anyone know of anyone in the UK who sells bicycle cards that are shimmed throughout the card please? I managed to purchase a couple of cards that are just shimmed in the centre of the card which makes it nigh on impossible to shift with a PK ring if the card is near the bottom of the deck. I'm assuming if the shim covers most of the card it will work with a decent PK ring wherever it is in the deck.