This flat iron rod has a button on one end. You can use
an action to press the button, which causes the rod to
become magically fixed in place. Until you or another
creature uses an action to push the button again, the
rod doesn't move, even if it is defying gravity. The rod
can hold up to 4,000kg of weight. More weight
causes the rod to deactivate and fall. A creature can use
an action to make a DC 30 Strength check, moving the
fixed rod up to 2m on a success.

Immovable Rod
Wondrous item