No Penetration Contact Set

Hi,

I am using SolidWorks Simulation and want to set up a 'No Penetration' type of contact option. One surface is of a composite material and the other of a titanium alloy. I wondered which is the correct way to set it up ie. which surface do I select for the Set 1 [marked blue colour] and surface for set 2 [marked pink colour] in the property manager.

I guess this question of mine may sound basic but I know in some simulation / FEA softwares it makes a difference and wanted to clarify.

Thanks

DSA

SolidworksSimulation