Question
Displacement in point out of 3D modeling
Hello!
Supposing to have square with hole,
I would like to fixe to the ground constraint at the middle of your length
and at the center of the internal circumference (as show in image below)

I thought to create an external point
,
then create a rigid link between internal surface and the point 
When I try to insert a displacement on the point, I obtain this error message

What is the error?
Thank you
Good Week!
Federico

