how to tell what layer you collided with on unity code example

Example 1: unity check collider layer

function OnCollisionEnter(collision : Collision)
 {
     if (collision.collider.gameObject.layer == LayerMask.NameToLayer("LAYER_NAME"))
     {
          Debug.Log("Touched a rail");
     }
 }

Example 2: checking a gamobjects layer

if(gameObject.layer == LayerMask.NameToLayer("LAYER_NAME")){}