In case you want to put the magnets where it is difficult I used this technique, Did this after following keystone Ed's thread.
Installed them on a switch. using Kadee 2 magnets not 4, and 4 super magnets. The first photo shows the Kadee magnet and the four super magnets underneath, also notice that they are not parallel to the rail or the same distance from rail. because of this it does NOT work as well as it should. This is on the fix it list. The stone, is a marker. This is a difficult location to install. The other pics shows the correct way, magnets parallel and same distance from rail.
Clem