If you decrease the area of the surfaces in contact, how will this affect the force of friction?
One rather counter-intuitive feature of the force of friction is that, to a first approximation, it does not depend on the area of the surfaces in contact.
A simple model of what's happening at the microscopic level helps us understand this. Viewed under a microscope, a surface generally looks rather rough, with hills and valleys. When you put two surfaces together, they actually make contact at very few places. When trying to move surfaces past each other, the high parts on each surface get stuck on one another.
Something about the interaction between the surfaces must have changed when the surface area decreased. The force is certainly the same. What changed?
With the same force, decreasing the area increases the pressure, basically squishing the surfaces closer together. Things balance so the force of friction is the same.