Side Scroller Platforms

Hi there, i am making a Basic Side Scroller but i am having issues with the Platforms.
What i am trying to do is make a Platform like in the Game Terraria, but in order to Stand on it, you have to hold Z on your keyboard. Otherwise you fall through it.
I am using Block All and Overlap All as collision modes for this, but i am having a lot of Issues with it. If you can help, thanks.