Watch batteries inevitably die. Obviously, as the battery slowly fades, your watch loses time, and you're left with the task of replacing the watch's battery. Usually, this is a simple endeavour, especially if you own a watch with a snap-on back. However, if you own a watch with a hatch back or screw-on back, your job is a bit more difficult. In fact, a watch with a screw back will require a special tool known as a case wrench.
Examine the back of your watch; look for any rubber gasket that may be in place. If you see a rubber gasket or ring, make sure it is lined up with the case of the watch. In order to be lined up correctly, the ring or gasket must be fitted snugly around the circumference of the watch case. If the gasket/ring is not lying flat or fitted correctly, the back cover will not snap on as it should. Place your watch face down on a soft cloth.
Look for a small indentation on the back cover of your watch. If you see an indentation, line it up with the winder on your watch. If you see no such indentation, simply place the cover on the back of the watch.
Place your thumbs at the 3 and 9 o'clock positions on the back cover and firmly press down. Make sure you use an even amount of pressure on both sides. The cover should snap into place. If not, you need to take your watch to a professional, as a case vice will be needed push the back onto the watch body.
Position your watch face down on a soft cloth. Look for any rubber gaskets or rings and make sure they are properly lined up with the case of the watch. Again, the ring or gasket needs to be fitted around the circumference of the watch case and be laying flat against the case. If misaligned, your back cover will not attach as it should.
Use your fingers to start the screw that holds the back cover in place. Turn the screw clockwise as far as you can with your fingertips. A hatchback watch usually has one or two small screws which hold the back cover of the watch in place.
Find a small coin, such as a penny or dime. As you'll see, the screw has a slot in it which allows you to use a coin or small screwdriver to loosen and tighten it. Use the coin to finish tightening the screw. Turn the screw until it is tight, but do not use excessive force, as you risk stripping the threads on the screw.
Examine the back of your watch and look for the presence of any rubber gaskets or rings. If present, make sure they are correctly lined up with the case of the watch. Once more, a properly aligned gasket or ring will lie flat around the circumference of the watch case.
Lay the watch face down on a soft cloth. A screw-back watch will have threads on the back cover itself. Most screw-back watches will also have four tiny slots on the back cover. Take the back cover between your fingers and start it on the case of the watch, turning it in a clockwise manner. Make sure you start it evenly. If you find it difficult to turn the cover, it may be cross-threaded. In this case, remove the cover and start it again.
Line up the notches on the wrench with the four small slots on the back cover of the wrench. Once the wrench is securely attached, finish tightening the back cover of your watch.