What's the best way to implement 2D stairs and crates in a game, similar to classics like Dangerous Dave 2?

Question

2D

I've been scratching my head, nothing comes to mind. What would be a better way to implement 2D stairs and crates in the game, similar to classics like Dangerous Dave 2?
Explanation: these blocks in the game are transparent on one side for movement, but when falling under the influence of gravity, we can stop on them.
Example 1. We
stand under the box

We jump - and find ourselves on the box

Example 2. We
stand under the stairs:

And we can jump to any step of the stairs, from it - to any next, and so on.

But at the same time, we can hold down + jump and jump to the platform below.
I can't figure out how to bring this together with the Unity physics engine, because if it registers a collision, it won't let you move on.

Answer 1

Have a look here:
answers.unity3d.com/questions/50518/passable-one-s...
Also might be useful:
answers.unity3d.com/questions/362021/eficient-one-...
forum.unity3d.com/threads/ 71790-layers-collision-a... (a-question)