Currently, you are only able to lock and unlock your own physical and/or virtual card, not anyone else's card. To do so, please follow the steps below:
Step 1: Launch the Brex app
Step 2: Click on the card at the top of the Home page; if this is not the card you want to lock, use the swipe on your phone to find the one you are looking for
Step 3: Click on Lock card or Unlock card (depending on the current status)
Once the card is successfully locked, the card graphic will be greyed out and a Locked status will be added to the top-left of the card.