Preparing your trunk(s)
You can bring your own bags or suitcases for your supplies, or an old suitcase which you may want to leave there. However, most volunteers use a plastic footlocker. This one (below), available at Walmart, is made by Sterilite and costs about $20 from Walmart. Other retailers sell it for much more. It has wheels on one side and different handle points to make transport easier. It also has fairly secure latches so it won't pop open. Here is a link to it at the store (set of 2). Adjust your location to see if it is in stock locally.
Please see the photos below for some suggestions on how you might want to prepare your trunk to make it look official and hopefully you will slide through customs easier.
I like to make a handle for the end since I am taller and when using the wheels, the handle on the trunk is a bit awkward. See the photos here for a quick and easy way to do that with inexpensive supplies you can get at Walmart when picking up the trunk.
I also put this little sign on the trunk on 3 sides (top, one end, and one lone side). I secure it with clear packing tape (grab some at the store while you are there).
I also put some cable ties on the top next to the lock hole so after it goes through TSA at the airport, they can attach a cable tie through the hole. You don't need to, but I find it is useful so no one in the baggage decides to pop it open quick and pilfer something!
If you would like to make an easy to use handle that allows the trunk to also work as a dolly or allow you to not have to lean over to pull it, follow the below photos. You can buy some "Paracord" (thin, strong cording or rope) in the home improvement section of most Walmarts for a few dollars. I recommend doing a double pass and just tying a secure knot on the inside. If you pass it so the knot is on the inside as in the pictures, it is more sturdy. I like to use a small peice of PVC pipe for a handle so the cord doesn't dig into your palm. A small peice of rubber hose or tubing works fine.
There are a lot of ways to do it, but this is an easy, no tools way.
You can even stack two trunks on top of each other, then use the top trunk's handle to pass through the lower trunk's handle (as in the photo) and carry two trunks at once much easier.