RE: Stand alone 'fridge/freezer boxes

Indeed these various stand alone 12v/110v refrigerator boxes look tempting,
a little easier to install than something like the Norcold, store it out of
the van when not in use, etc.  But one big (at least o me) question:  How do
you secure it, keep it in place?  Having once rolled a Westy this tends to
come to my mind a little quicker than others.