The shield can give ... itself ... cover?
Incepshield.
A tower shield can give cover to you and all your equipment. A tower shield is part of your equipment. Do the math.
The shield can give ... itself ... cover?
Incepshield.
Except against spells. Which is why it's not all that great. Plus, Rule of Siege Weapons; You do not get cover against Siege Weapons, unless said cover is at least three feet thick and made of stone.
1. *checks* That makes no sense. I'd give you cover from spells from a cover shield in the same way I'd disallow tower shields covering themselves: By saying "Ignore that bit".
2. I dunno, a foot-thick piece of metal seems like it would work. Or, really, a foot of stone. Or five feet of turf. Or a gullible hill giant.
Or yo' mama.
Check it out:
Buy 6 tower shields
Buy some nails, 2 hinges, and a hammer
=
Inexpensive house! With hardwood flooring.
Wouldn't work. Tower shields are not square.