Using a context bound in a class type parameter

I was under the impression that context bounds would work only on methods:

trait Target[T]

class Post {
  def pinTo[T : Target](t:T)
}

apparently context bounds can be used in class too (but not in trait):

trait Target[T]

class Post[T: Target] {
  def pintTo[T](t:T) 
}

Now I'm confused as to how the evidence can be provided to Post?

class Business
implicit object ev extends Target[Business] // is implicit necessary here ?

val p = new Post[Business] // ?? how do I provide ev ? 

related to Modeling a binary relationship between two types