I built 10 flag holders for our balcony.
My father had the manual skills, I had the idea and supermagnete.de the right magnets.
The wooden flag holders are hand-made and have 4 pot magnets CSN-25
embedded on the backside, which provide for an adhesive force of about 68 kg and protection during wind gusts.
The magnetic holders are attached to the vertical metal bars of the balcony.
Experience has shown that the flag holders don't move even during heavier winds.
The wooden slabs that the flags are attached to are the weak links as they break during heavy wind gusts.