This guide is for models using hinge type K22. This hinge type is used in the following models:
Some colors in the pictures may differ for your model. That is fine, what matters most is the shape of the hinge piece.
The plastic hinge mechanism must be oriented as shown for it to fit onto the metal keyboard hooks.
Hook the inner bottom edge of the hinge under the bottom metal hooks on the base of the keyboard.
Tuck the top of the hinge into place, one side at a time. In this example, the top right side has been secured first. The top right and left tabs of the plastic hinge should be hooked under the metal hook protruding from the base of the keyboard on each side. You can now check that the hinge works by flexing it up and down; it should pivot easily at its axis.
Align the key on top of its place on the keyboard, and press down evenly. All four corners of the key should click into place.