Tower Shield Total Cover with no proficiency

[Nanaika]

Could a character not proficient with tower shield use it to get total cover (as a standard action)

I don't see from the feat description or the item description that this use is restricted to those who are proficient.

I understand that the character using it this way would get a significant penalty to skill checks and to attack rolls, but I just want to know if it can be done.

[Brett Johnson]

I don't see why not. They'd suffer major penalties to their attacks and skills.