Ask the Experts / Benchs or Lamp on Invisible Path

Hello, I need some help. Sorry if it's already explain somewhere I searched and didn't find. I see in many parks benchs or lamps on invisible path but I cant' do this. I use OpenRCT2 and I tried a lot of things ( tile inspector... ) but nothing works. How do you this ?

 

Thanks !

Enable height markings on path, then hover your mouse over the height markings.

Thanks for this quick response ! Raaa I knew it was a simple trick but impossible to find it myself ! As a riddle when somebody give you the solution !