Using a spudger or small flathead screwdriver, gently break the seal between the white plastic backing and the metal top near the missing foot opening.

Pry up the corner slightly to allow the foot to be replaced.

Place the rubber foot back in place.

Squeeze closed the backing and metal top (it will snap into place).

Click on trackpad to test.

Insert the battery and screw the battery cover closed.

A foot may again dislodge, for example when you inadvertently move a sheet of paper under the trackpad. Repeat steps as needed to replace.