Question about fortified tanks...

[Night Owl]

Firstly, I am no WWII historian (but I'm learning!)

I recently picked up the PSC Allied Sherman M4A4 / Firefly box in 1/72.  To my surprise the sprues come with two slightly different hulls and turrets, one for each make.  My first thought was "cool, I can model casualties as well.". The more I thought about it, however, I realized I could make some nicely fortified tanks hunkered down in trenches and camo.

I've scoured the web for a few days and can't seem to find much about fortified tanks, much less any account of Allies practicing this. 

I have seen evidence of both Axis and Russian accounts of this practice, even to the point of mounting turrets on top of bunkers.

So my question - Does anyone know of a time when Shermans were fortified and/or entrenched or were they always on the move vs. the resistance?

I suppose I could always mount them on mech legs for Weird WWII but that would be, well, weird:-)

Thanks in advance for your help,
Night Owl