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 bottom-right corner.
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 Centre, Launchpad or Lock Screen.
To use one or more modifier keys with the hot corner, press and hold the Command, Shift, Option or Control key while viewing the pop-up menu.
When you’re done, click OK.
When you move the pointer to the selected corner of the screen (and use a modifier key, if you set one), the selected action starts. To stop the action, press any key, move the mouse or touch the trackpad.