When you apply a muscular force with a hammer to drive a nail into a wall, the force that primarily fixes the nail in the wall is friction . As the nail penetrates the wall, frictional forces between the nail and the material of the wall resist the nail's movement, helping to hold it in place. Additionally, the normal force from the wall material, which acts perpendicular to the surface of the nail, also contributes to keeping the nail fixed by increasing the frictional force.
