From underneath I run a thin blade around the join to break any ‘side’ weld, it sinks in about 4-5mm, careful not to lever or push too hard as you’ll leave a line visible in the outer plastic. Then I use a right angled tool in one of the four holes to ‘carefully’ prise it open, and work around the other holes too. There are four weld points each side, and two at each end. With a remote switch you have to be careful not to cut any of the turns of copper that make up the electromagnet(plug end), or to break the soft magnetic part on the spindle at the other end. With the manual point motor you can be a little less careful!