Spiked

When you succeed on a Strength (Athletics) check to shove or trip a creature while wielding a shield with this property, the creature takes kinetic damage using the spiked damage (which appears in parentheses with the property) + your Strength modifier. If you use a shield with this property as an improvised weapon, the damage increases by one step (from d4 to d6, d6 to d8, or d8 to 2d4).