About the Z mount 🇫🇷

Hi to you

Questions around the Z sled.

I wonder if the lower bearing  really can ensure that the threaded rod does not move upwards when there is pressure on the spindle.

There is nothing at the top that holds the threaded rod down.

The lower Ball bearing.. whats the name / type / model of that ?  I really cant find it anywhere

Kind regards

Lars, Denmark