Thank you for the screenshot
This mechanic is standard so we did not think to explain it, may be we should have.
Press down and jump to go throught wood platforms. I will post about the mechanics of the game in another comment.
Viewing post in Twilight Fortress jam comments
Now that you say down and jump that makes a lot more sense with the animation you included. However, I am used to playing games where going through the platform is just pressing the down button but honestly, I can see how adding the jump button can prevent you from going through the platform unintentionally. Thanks for bearing with me while I tried to figure this out!