How do I remove this unusual floor-mounted magnetic door stopper from a paving slab?

I have a floor-mounted magnetic door holder / door retainer / door stopper with adjustable hex stem on my balcony that I need to remove so I can position a new garden shed.


It has a stainless-steel magnetic head and what appear to be three hexagonal extension sections underneath. At the bottom there is a washer/flange sitting against the paving slab.


I have tried:

• turning the whole column anticlockwise;
• holding one hex section with one spanner and turning another with a second spanner;
• trying the different hex sections individually.

Each hex section seems to rotate to some extent, but then becomes tight again. If I turn the whole assembly, the whole column appears to rotate rather than unscrewing from the floor.


There is also a female threaded hole in the top of the magnetic head, but I can’t see an Allen/Torx screw inside it.


I cannot lift the paving slab because an existing shed sits on most of it, so I need to remove the stopper from above if possible.


Does anyone recognise this type of door stopper or fixing?
Is the bottom likely to be an expansion anchor, threaded insert, or some sort of concealed fixing?
Is there a particular tool or removal technique I should try before I call a handyman?


I’d ideally like to remove it intact rather than cut it off.


Thanks

Use an open-ended spanner or locking pliers or mole grips on the long hexagonal shaft. Turn it anti clockwise. On many designs, this hex section simply acts as a coupling nut that threads directly onto a fixed threaded stud sticking out of the floor.Loosen the bottom nut: If the entire shaft spins along with the bottom bolt without unscrewing, use a flat spanner to hold the very bottom thin nut (highlighted by the red circle) while you unscrew the hex shaft.

crank39 said:

Use an open-ended spanner or locking pliers or mole grips on the long hexagonal shaft. Turn it anti clockwise. On many designs, this hex section simply acts as a coupling nut that threads directly onto a fixed threaded stud sticking out of the floor.Loosen the bottom nut: If the entire shaft spins along with the bottom bolt without unscrewing, use a flat spanner to hold the very bottom thin nut (highlighted by the red circle) while you unscrew the hex shaft.

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Thanks, that makes sense. I think this may be exactly what’s happening — when I turn the long hex shaft, the whole assembly seems to rotate rather than backing out from the floor.

I’ll try holding the very bottom thin nut/collar with a thin open-ended spanner while turning the lowest hex section anticlockwise with another spanner.

Do you think that bottom piece is definitely a locking nut/collar rather than just a washer? And would a thin cone spanner be suitable if a normal spanner is too thick to fit?