Receive damage if collided only with the top side of the 3d box collider

I want my player to receive damage if he collides with only two sides (top and bottom) of a box collider. This is the code I use, but it detects when the player is collided with any part of the collider.

private void OnColliderEnter(Collision collision)
{
    GameObject hit = collision.gameObject;
    PlayerHealth health = hit.GetComponent<PlayerHealth>();
    if(health != null)
    {
        health.TakeDamage(10);
    }
}

There is a simple way to solve this:

 private void OnColliderEnter(Collision collision)
 {
    if(collision.transform.position.y > transform.position.y || collision.transform.position.y < transform.position.y)
    {
     GameObject hit = collision.gameObject;
     PlayerHealth health = hit.GetComponent<PlayerHealth>();
     if(health != null)
     {
         health.TakeDamage(10);
     }
     }
 }

I haven’t tested that, but it should work.

this seemed like a fun challenge so I went ahead and included my solution for it; tested and affirmed. I commented out the unused namespaces, so be aware of that. lastly I commented most every line of my code so you may understand why I did things the way I did. if you choose to use my solution, let me know if you run into any problems!

//using System.Collections;
//using System.Collections.Generic;
using UnityEngine;

public class CollisionDamageBySide : MonoBehaviour
{

    // Private
    private Collider collider3d;

    // Awake is called before start at object initialize
    void Awake()
    {
        collider3d = GetComponent<Collider>();
    }

    // Collision detection
    void OnCollisionEnter(Collision collision)
    {
        // ensure collision prior to logic - best practice
        if (collision != null)
        {
            // reserve collision collider
            Collider cc = collision.collider;
            // reserve collision point of contact
            Vector3 cp = collision.GetContact(0).point;

            // determine if collision to player
            if (cc.tag == "Player")
            {
                float xMin = collider3d.bounds.min.x; // for code cleanliness
                float xMax = collider3d.bounds.max.x; // ...
                float yMin = collider3d.bounds.min.y; // ...
                float yMax = collider3d.bounds.max.y; // ...
                float zMin = collider3d.bounds.min.z; // ...
                float zMax = collider3d.bounds.max.z; // ...

                // ensure player within x boundaries
                if (cp.x >= xMin && cp.x <= xMax)
                {
                    // ensure player within z boundaries
                    if (cp.z >= zMin && cp.z <= zMax)
                    {
                        // ensure collision is either top or bottom
                        if (cp.y >= yMax || cp.y <= yMin)
                        {
                            // replace this line of code with your custom damage method
                            Debug.Log("Processing damage!");
                        }
                    }
                }
            }
        }
    }

}

Ummm… Probably a laughable comment and fraught with mistakes and much too late…But…Why not place a collision envelope where it is required…or two of them?
Can’t that be done? Use a box or a mesh collider…scale it to fit etc etc…