You can skip this step if you bought your putty knife from iFixit. Putty knives purchased from iFixit come with pre-ground edges.

You'll need a putty knife in order to open the case. A 1.5 inch thin putty knife will work well, but you'll want to grind the edge down. Rub the putty knife's short edge back and forth on a sheet of all purpose rough grit sandpaper (100 grit will work fine) until it attains a beveled edge.

Carefully insert a putty knife into the crevice in between the top cover and bottom housing. Start on the left side first. Push the blade down until you meet firm resistance (roughly 3/8 of an inch).

Gently enlarge the existing crevice by prying the handle of the putty knife downward and away from the mini.

It helps to start in the middle, then work along the edge until the bottom housing pops up slightly.