This kind of skills are usefull if you use shield in a battle. There are 4 lvls of shield skills.
Shield skills 1st lvl
Enchance attack speed when equipping a shield.
Increase party members' physical resistance and decrease magical resistance for a limited time. Mp cost: 300.
Shield skills 2nd lvl
Bash with the shield. You have a chance to stun the target. Need to learn shield mastery lvl 5 for this skill. Mp cost: 100