I made this instructable as a way to help transport books with some pretty common supplies that are easy to find from things leftover boxes or for things like the support cardboard you can look in boxes for big projects. The structural cardboard can be hard to cut which is why you may need to use a saw.

NOTE: The balance point may vary due to how many books you put in and always put the bottom books in first to help the shelf last longer.

Supplies

A box that is 22 inches by 15.5 inches when upright
4 corners of structural cardboard that are each 7.5 inches long
2 rectangular pieces of support cardboard that are each 27.5 inches long
Two sets of wheels(you can also use skateboard wheels or something similar)
A piece of cardboard that can be 9-10 inches wide depending on how long you want the lip and 21 inches long
4 legos that are the the same size to use as latches
5 inch long corner piece of structural cardboard
29 inch long corner piece of cardboard
Hot glue gun with extra glue sticks
Measuring tape
Cardboard cutter
Pen or
Optional: Paint
And finally as many books as your shelf can hold

Step 1: The Shelf

To start you want to put the shelf in, start by putting the shelf about in the middle. Once its in the middle you want to glue the 7.5 inch corner pieces like so, you want to glue the left side on two of them the right side on two of them and the top for one right and left and the bottom to a left one and right one. When you have glued each corner piece you are ready to attach them to the build. You want to make sure each corner piece is securely attached to the side and shelf. Now once you have finished putting in the shelf you'll be ready to add wheels.

Step 2: The Wheels

For the wheels you will want to use your set of wheels and the two 27.5 inch long pieces of cardboard and when you have every thing ready you will want to glue the two pieces of cardboard on to the wheels but make them apart so that they have enough surface area to hold the bookshelf up. Before you attach the wheels you should put in an average amount of books and test where the balance point is for you the you should mark that spot with your pen or pencil and then after you take out the books flip your book over and glue your wheels to line up with that spot then once you glue the cardboard apply pressure so that the wheels don't fall off. then you can move on to making the latches and removing the side flaps.

Step 3: Latches

For the latches you will have to use the legos to make them, you will have to start by making a small cut half way through the bottom and top flaps allowing you to fold them over and glue them as half flaps. now you'll notice they don't stay on the box so you want to glue the first lego with the knobs to a side bottom or top flap (you can do either one first.) and then lightly attach the second one to the top lego so you can line it up then you will glue the bottom lego down after lining it up. Repeat this again on the top or bottom to finish the latches and then we can move to the handle.

Step 4: The Handle

For making the handle you will need to use your 5 inch long corner piece and your 29 inch long corner piece to put it together. You first need to put the 5 inch piece a bit past the middle of the box and glue it down. Next you will have to take the 29 inch piece and glue it down. When putting the main handle on you will have to choose what angle you want it at by changing how far from the edge it is while on the 5 inch piece. Next you're ready for the finishing touches.

Step 5: Finishing Touches

For the finishing touches you can do several more things. One of these things that helps cleanup the look based on your cardboard is to paint your bookshelf, While I did not this it is always a good option. The second option is to cut off the side flaps as they can be annoying and get in the way but you can keep them if you like the look they give, and finally you can fill it up with as many books as you can.

Congratulations You have successfully built a portable cardboard bookshelf! I hope you enjoyed my instructable and had fun building it!