So the purpose is to lock the engine when trying to unscrew the starter cup or flywheel nuts. - OK, I can see that, but I would be a little apprehensive to use a tool like that for that purpose. Don't want to mess up my piston. Thanks for the info
Here is what I have done so far. Installed new cam gear and made sure timing is dead on according to manual. Compression release nipple on cam is moving freely in and out when pushed manually. Valve lash is 0.10 mm (using Stihl gauge and adjusted and checked when engine is cold). Engine starts...