Simulation constraints to allow displacement in positive direction but not negative

[misc_engineering]

I am designing a shelf which will be bolted to the wall. This will have 2 screws and 2 struts to support the shelf. Picture a typical closet self with a particle board top and brackets beneath. How do I tell fusion that the face which is against the wall cannot move in the negative y direction do could move in the positive y. I only see the option to lock that face for both positive and negative directions. 

[shekar_sub]

Hi Matt,

The closest that I can think of is Prescribed Displacement constraint with a positive distance. Please see attached image. Does this work?

https://help.autodesk.com/view/fusion360/ENU/?guid=SIM-PRESCRIBED-DISPLACEMENT-CONCEPT

Thanks

Shekar