Your shell is your shield.
Prerequisite[]
Tortle, Fortify shell, Shield Focus, Con 15, Dex 15
Benefit[]
Your maneuvers allow you greater ability to defend with your shell. You may apply any feat normally usable with a shield through your shell. If attempting a shield bash, your shell deals damage as though it were a heavy shield. For feats such as Shield Specialization, shell is a category separate from buckler, light, heavy or tower. This does not allow you to enchant your shell as though it were a shield via the Self-Armored feat, only that it is usable like a shield at times. If you are wielding a shield, all shield abilities work through the actual shield and you cannot apply them to your shell at the same time (such as applying Shield Focus twice or similar stacking shield bonuses).