This script is about putting items in slots

SelectionManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.Events;

namespace CraftingSystemRework
{
	public class SelectionManager : MonoBehaviour {

		//object selected
		public GameObject selectedObject, lastSelectedObject;
		public GameObject selectedSlot, lastSelectedSlot;
		public GameObject rando;
		public Slot selectedSlotscript;
		public CraftSlot selectedCraftSlotscript;
		public Inventory inventory;

		//keeps checking if you deselect
		void Update ()
		{
			CheckInput();
		}
		//checks if you deselect a item
		public void CheckInput ()
		{
			if(Input.GetButtonDown("Fire2"))
			{
				Deselect();
			}
		}
		//selects an object and making references to its parents scripts
		public void Select (GameObject go)
		{
			if(selectedObject != null)
			{
				lastSelectedObject = selectedObject;
			}
			selectedObject = go;

			selectedCraftSlotscript = selectedObject.GetComponentInParent<CraftSlot>();
			selectedSlotscript = selectedObject.GetComponentInParent<Slot>();
		}
		//makes the select object null
		public void Deselect ()
		{
			lastSelectedObject = selectedObject;
			selectedObject = null;
		}
		//childs the item to a slot if the slot is empty
		public void ChildItem (GameObject go)
		{	
			if(selectedSlot != null)
			{
				lastSelectedSlot = selectedSlot;
			}
			selectedSlot = go;

			if(selectedSlot.tag == "Slot")
			{
				if(selectedSlot.gameObject.transform.childCount == 0)
				{
					selectedObject.transform.parent = null;

					selectedObject.transform.SetParent(go.transform);

					selectedObject.GetComponent<Item>().Checks();
				}	
			}
			if(selectedSlot.tag == "Craft Slot")
			{
				if(selectedSlot.gameObject.transform.childCount == 0)
				{
					selectedObject.transform.parent = null;

					selectedObject.transform.SetParent(go.transform);

					selectedObject.GetComponent<Item>().Checks();
				}
			}
		}
	}
}