Question: Open a modern quartz movement watch to replace the battery.
Options:
Place the watch face down on a soft surface. Look to see the back is a screw on or a push on.  Unscrew a screw on with the appropriate tool.  Use a small screw driver to pry the push on type off.  Put the new battery in place and reassemble.
Place the watch face down on a soft surface. Look to see the back is a screw on or a push on.  Unscrew a screw on with the appropriate tool.  Use a finger nail to pry the push on type off.  Put the new battery in place and reassemble.
Answer: Place the watch face down on a soft surface. Look to see the back is a screw on or a push on.  Unscrew a screw on with the appropriate tool.  Use a small screw driver to pry the push on type off.  Put the new battery in place and reassemble.