Using a curved blade minimizes the chance of scratching the case or cracking the glass. Only pry with the curved section of the blade, and not the tip or flat section.

Place the curved section of the blade in the gap between the glass and case on the lower edge of the watch face, and press firmly straight down into the gap.

Be very careful to maintain complete control over the knife—once the gap opens, if you're pressing too hard on the knife it may slip in and cut the battery.

This should wedge the gap open and cause the glass to lift slightly up from the case.

When the glass has lifted, gently rotate the knife down, opening the gap more by pushing the glass up.