Symbolism, Imagery, Allegory
For most of the book, Jess and Leslie get to Terabithia "by swinging across [the creek] on this enchanted rope" (4.102). In a series of tragic coincidences, the rope gives out when Leslie is swinging on it by herself and when the creek is completely full. The danger Jess felt but couldn't express comes suddenly, horribly true. It's nobody's fault, but it can't be undone. After the tragedy, Jess wonders if their magic land is still magical, "If it was still Terabithia. If it could be entered across a branch instead of swung into" (13.5). It takes him a while to figure out that it is, and it can – and that not going back to Terabithia would be a disservice to Leslie. Yet, after his close call with May Belle, Jess realizes there has to be a better way, a new way, into Terabithia:
"The next day after school, Jess went down and got the lumber he needed, carrying it a couple of boards at a time to the creek bank. He put the two longest pieces across at the narrow place upstream from the crab apple tree, and when he was sure they were as firm and even as he could make them, he began to nail on the crosspieces." (13.69)
As if Leslie's memory wouldn't be present each time Jess went to Terabithia, he's ensured a memorial to his dear friend by using lumber from her parents' house to build the actual bridge. The bridge Jess makes doesn't look like much: although Jess knows it's "the great bridge into Terabithia," he understands it "might look to someone with no magic in him like a few planks across a nearly dry gully" (13.82). But it's another way of bringing the magic Leslie saw in Terabithia to the outside world where he can share it with others. (For more on the bridge's significance, see "What's Up With the Title?" and "What's Up With the Ending?")