Blocking Days in Outlook

Blocking days works the same as blocking hours, you just have to mark the event as lasting all day.

Create a new event.
Fill out the details and mark it "All day" and busy, so Lisa knows you won't be around.
Save the event and then make sure to DECLINE any remaining showings that day. Declining is important because some people want to block a whole day for paperwork, but don't mind having a showing or two. Lisa doesn't want to nose into your personal business, so DECLINEing established appointments is between you and your boss.

Remember to DECLINE appointments you can't make, even during blocks. Blocks only stop new invitations!