Use hot corners on Mac
You can use the corners of the screen as hot corners, to quickly start actions when you move the pointer to a corner. For example, you can start the screen saver when you move the pointer to the top-left corner of the screen, or lock the screen when you move the pointer to the top-right corner.
Tip: By default, the bottom-right hot corner is set to Quick Note, so you can quickly open a note to jot down your thoughts at any time. See Create or edit a Quick Note.
On your Mac, choose Apple menu > System Preferences, then do one of the following:
Click Hot Corners.
For each corner you want to use, click the pop-up menu, then choose an option, such as Notification Center, Launchpad, or Lock Screen.
To use a modifier key with the hot corner, press and hold the Command, Shift, Option, or Control key, or a combination of these keys, while viewing the pop-up menus.
When you’re done, click OK.