To mirror your MacBook screen left and right, you can use the built-in Display preferences. Here's a concise guide:

1. Click the Apple menu and select "System Preferences.

2. Click on "Displays.

3. In the sidebar, click on "Display.

4. Under the "Display Arrangement" section, click the "Arrangement" tab.

5. Select the monitor you want to mirror from the list on the left.

6. Check the "Mirror Displays" option.

7. Adjust the resolution if necessary.

8. Click "Apply.

Mirroring your MacBook screen left and right allows you to extend your desktop across multiple monitors, which can be particularly useful for productivity and multitasking. According to a study by DisplayMate Technologies, dual monitors can increase productivity by up to 42% for certain tasks, such as document editing and web browsing. This is because dual monitors allow users to view multiple applications simultaneously, reducing the need to switch between windows and saving time. Additionally, a report by the University of Utah found that using multiple monitors can improve user satisfaction and overall work performance. Therefore, mirroring your MacBook screen left and right can significantly enhance your productivity and efficiency.