Step 1
Unplug the microwave and place it on a large, flat work surface -- such as a table.
Step 2
Examine the microwave door to determine whether the top or bottom screw is the loose culprit.
Step 3
Tighten the screw on the top of the door by opening the microwave door, inserting the screwdriver into the screw and turning it. You will need to turn the microwave carefully on its back if the loose screw is on the bottom of the door.