By putting the paper clip
disable the giant magnet in mission 3
Dismantle the giant magnet on the roof of the building.
in the hq
you get a magnet
key
you don't turn it off
You go to the Iceberg and use the magnet to get the springer that's frozen in ice.
On the ceiling of the vault because of a giant magnet caused by Herbert!!
Next to the Gadget room and the lock code is key.
If You Mean The Epf Mission You Open The Magnet With Your Wrench Then Put The Paper Clip In The Magnet Box
you tickle it with the duster than follow it
Go to the Roof (using the key), use your wrench on power box then get your paper clip and you will turn off the giant magnet!