There are so called the Mark IV left/right turn switches in Altas RR website. As the photo shows no switch at all on the switch itself, how do you control the turn? Also, under what circumstances should I use the Mark IV switches as opposed to the typical manual/remote swiches?
I can’t say I’ve used the Mark IV’s, but the customline turnouts have a throwbar with a hole in the center and a T-shaped extension on one side with some more holes. You have to add your own switch machine and link it to the turnout. I used Caboose Industry ground throws, but Atlas makes an above-board solenoid-driven machine, and I think an under-track version. You can also use Tortise machines and probably several others.
There is no provision on the Mark IV turnouts for mounting a double-solenoid switch motor. Mark IV turnouts are intended to be used with the Atlas under-table switch motors, a ground throw, or slow-motion motor such as a Tortoise.