Source: Unearthed Arcana 73 - Feats

You’ve trained in the effective use of shields. You gain the following benefits:

• Increase your Strength, Dexterity, or Constitution score by 1, to a maximum of 20.

• You gain proficiency with shields.

• In combat, you can don or doff a shield as the free object interaction on your turn.

• If you have the Spellcasting or Pact Magic feature, you can use a shield as a spellcasting focus.