The first step listed on switch machine instructions is:
1. Temporarily mount turnout using the centering yoke to lock points at center.
What is the centering yoke?
It's a u shaped piece of plastic they include with the kit so the track switch component is perfectly centered. When you buy the switch machine, it's calibrated to have that rod set perfectly centered out of the box so you can properly line it up with the track above
To be honest, I don't think you really need it if you can't find it. On your track, move the switch piece to the center As best you can. That's where the hole is then drilled. Their switch machines have wide tolerances so you'll be OK, even if it's not absolutely perfect
Additionally theres how-to videos on YouTube for this product.
It looks like the thing my red arrow is pointing to:
Turnout_Actuator_Walthers by Edmund, on Flickr
Walthers Photo
NorthsideChiTo be honest, I don't think you really need it if you can't find it.
In nearly all the Walthers/Shinohara turnouts I have when it came time to install the Tortoise from below I simply, and gently, wedged a pair of wooden toothpicks on either point to center the throwbar.
Hasn't failed me yet.
Good Luck, Ed
If you're using cork or other soft roadbed I find a a pair of push pins work great. Just insert them between the outside fixed rails and the points and they will hold the points in a centered position while you line up and insert the servo or Tortoise from below. Place a piece of double sided carpet tape on the mounting surface of the actuator so you can retry if you get it misaligned. When it's OK, go back and insert the mounting screws. Easy.
Charlie - Northern Colorado
Just a quick note. I have 24 of these switch machines. They are reliable. There was recently a bad batch a year ago that had some issues not responding. So if you have some issues, don't get stressed making it work. Walthers was excellent with troubleshooting and replacing a unit. They work really nice otherwise.
gmpullman In nearly all the Walthers/Shinohara turnouts I have when it came time to install the Tortoise from below I simply, and gently, wedged a pair of wooden toothpicks on either point to center the throwbar. Hasn't failed me yet.
Rich
Alton Junction