How to pass through oneside of a object but land on the other?

What I want to do is be able to walk through a object on one side, but not be able to go back through it. I want this because the game I am making the character bounces through the object from below. I tried using planes for this, but it seems that when the character is midway it sometimes causes problems (i.e. the player is shoot out into space...). So what is the best way to address this problem?

I'm not sure whether this is the best way, but you could turn colliders of your object on/off or simply make them a trigger which will allow you to walk through them.

So you simply place an empty game object with a collider set to isTrigger on each side of your object and if the player is on a specific side, you either turn the objects collider on/off or change isTrigger for the object to on/off according to the side the player is on. You would have to adjust the position of the triggers on both side, so that the player doesn't trigger the object to become impassable while the player is still walking halfway through (or bouncing).

there are two available approaches 1 programmaticly check the current position of the character and if it's in the side that you want then bounce it else let it pass the object. 2 create different colliders around your object and write different codes for different siides. if you describe more about your setup, i can tell you more. do you use rigidbodies or triggers? is the character a character controller or not?