No matter how diligently you join the two pieces of the ruler, they do not join.

No matter how diligently you join the two pieces of the ruler, they do not join. Why is the attraction of molecules not affected in this case?

Firstly, because the distance of intermolecular interaction turns out to be larger than initially, and secondly, the contact area is small. Molecules simply do not attract each other, in addition, an air gap enters the junction. If you polish two bodies with a very precise polishing machine, and then connect them, only then it will affect the attraction of molecules, because the contact area will be larger and there will be no air gap.