A watch can be opened by removing the back of the case. However, there are different kinds of watch backs, each with their own methods of removal without the kinds of tools used by professional watch repairers.
There are three common types of watch cases: a screw back case, a pressure fit case, and a four screws case. A screw back case can be opened with a pair of scissors. To remove this kind, insert the tips of the scissors into two of the notches cut into the back of the watch case, and turn counter-clockwise. The back of a pressure fit watch back can be removed by fitting a flat edge, such as a knife, against a small tab or indent cut into the side of the back plate between the lugs of the watch. A four screws case can be opened by removing the screws holding it together with a properly-sized screwdriver.