Type support for bolt connection

Hi ,

I have an equipment secured on a plate by 2 screws at front and back.
Now the equipment is experiencing external force which is 16g forward.
So, when I do the FBD diagram. Should I use Fix-Fix or Pin-pin support.

Initially I use fix-fix support because there is a moment at the bolt because it is resisting the beam from being turn.
However some other people claim to use pin-pin. Could someone justify and clarify this confusion.

Thank you