At 13:25 when you move the keyhole forward what is it snapping to as there are no vertices on the section where the keyhole will eventually sit?
Kent snaps it on the Y-axis to this vertex:
It is already centered on the X-axis because of where the 3D Cursor was when he added the Circle.
You can center your circle by selecting it (and nothing else) and setting its X value to 0 here:
