Originally Posted by s&wchad

DO NOT use any tape. You can repair separated seams/corners with craft glue (Elmers) and some simple tools.

This is my box repair kit:



Apply a small amount of glue to each edge of the seam. Position the separated edges together, place a corner brace on the inside and clamp it in place. Let it set-up for a day before removing the clamps and braces. If necessary you can put a large rubber band around the outside of the box to pull the edges together.

This type of repair is reversible and causes no additional damage. I've saved more than a few boxes with this technique and the repair is barely noticeable.