To lock a laptop, the method depends on the operating system, but the most common and quick way to lock it is by using keyboard shortcuts: For Windows laptops:

• Press Windows key + L at the same time to instantly lock the screen.
• Alternatively, press Ctrl + Alt + Del and then select "Lock" from the options.

For macOS laptops:

• Press Control + Command + Q to lock the screen immediately.
• Alternatively, click the Apple icon in the upper left corner and select "Lock Screen."

Other options include setting up hot corners on macOS to lock the screen by moving the pointer to a screen corner or configuring the power button to lock or sleep the device. On Windows, you can create a desktop shortcut to lock the screen or use the Start menu and user icon to find the lock function. The locked screen will require the user to enter their password to unlock and regain access to the laptop. These quick methods ensure security when stepping away from the laptop temporarily. All these methods work without closing applications, just locking the screen until unlocked again with the password.