Why can't I use a D grade shield?

Hi!

I have a Bronze Shield (D grade) that has Pdef 101.Before I had a Bone Shield (no grade) with Pdef of 90.With this shield I had Pdef 188.When switching the new shield, nothing hapened.I still have a Pdef of 188.What hapened?Why this D grade shield makes no difference?
Thank you in advance!

Best regards!

Equipping a shield doesn't affect your Pdef. Wearing a shield gives you a chance to block, at which time if successful the block will reduce the damage taken. I think by the ammount of Pdef. given by the shield.

When you block a hit, your p.def sums up with your shield's p.def against this hit.

is D grade shied a basic one? i was trying to learn some basic idea of the game . maybe i will played later on

There are seven grade "levels" within L2 that have to do with gear availability.

Non-grade: Level 1 - 19
D Grade: Level 20 - 39
C Grade: Level 40 - 51
B Grade: Level 52 - 60
A Grade: Level 61 - 74
S Grade: Level 75 - 79
S-80 Grade: Level 80+

So long as you are at least the initial level, you can use gear of that grade. I hope this helps.