Item Mardigor's Frosty Tablet states in the lore "Frozen solid, so it can be used as a buckler". I can confirm, you can't. Its range only, and does not offer "Secondary slot" usage.
GNOMEPOWER has the idea, but my question is did you mean Margidor's Frosty Tablet? That drops off of Margidor who is a named skeleton in an icy zone. He mostly likely made it frozen so he could use it as a buckler to stave off adventures such as your self.