The connecting feet and supports were not supplied

I ordered the Gittet, but they were delivered without non-slip feet. How should I set this up exactly

Could someone tell me how high the hole is underneath? It would be for my rabbits and I want to make sure they don't get under it ;-)

Can this grille be fixed at a specific setting?

I am interested in this Trixie safety gate! Do I have to make holes to fix it? How do I fix it?