When designing the mount, it says to inset the inside by pressing I, then pressing B to set it to the boundary. But pressing B does nothing. Is there something I’m missing?
What we are missing is anything to go on.
Guessing in the dark with nothing to see, odds are extra geometry is there somewhere messing things up.
General Q&A note
Help us all to help you.
Please give full screenshots with any questions. With the relevant panels open.
Also, include the lecture time and name/number that is relevant to the problem/issue.
The screenshot can be done by Blender itself, via the ‘Window’ menu bar top left hand side.
On that menu drop down is ‘save screenshot’.
Close ups additionally where they help.