Rhino is very good for mechanical models to be ported to CAM and then CNC. That’s what I use it for. You might think that Rhino’s Solid tools are ideal for this work. You might think that all you need to do is create some basic solids, do some booleans, add some fillets and ‘Bob’s your uncle’, you’ve got something ready to machine. Bit that will only work if what you want to model is very trivial. If you take that approach to learning Rhino most of the time you will find yourself stuck and completely unequipped to get yourself unstuck.
I’m guessing that XXXX is one of the Solid tools.
There is nothing in the solid tool menu that you can’t do yourself using Rhino’s manual surfacing tools. The biggest advantage of learning to model without the solid tools is that you will have far more options for geometry creation and you will have more options to get unstuck when you get stuck.
If XXXX is not a tool from the solid menu look it up in the Help you should be able to figure out what you need to do to make it work
But
I’m guessing XXXX is a tool from the solid menu and your best bet is to find tutorials that do not use those tools. Learning to do it yourself is the only way you will quickly come to an understanding of what makes the solid tools work (or what makes them fail).