Pro-Tip: Do not overload the parts tray.. it can get very heavy! Just store handy electrical materials that are used often.
A parts tray can really make you shine as an apprentice! Often materials can be out of stock on a jobsite, or save you from walking to the jobsite trailor, or even if you’re an hour out of town.. a parts tray may have what you need! It’s wise to store lightweight commonly used electrician materials in a parts tray like Anti-Shorts for armored wire, different sizes of wire nuts, or wire connectors. You can buy a separate parts tray, but I personally like a Hand Tool Bag with a Parts Tray Underneath.