Get block behind?

How would I get a block behind a block?
For example the block a wall sign is on. Thanks!
I read the docs but can't figure how to

Like placing a sign on a chest?

Or simply a block

Ok just crouch down have the sign on your hand place it on the block.. then voila! GOOOAL. :,D

This is a plugin DEVELOPMENT section. People these days... *sigh*

Lol.. I didn't see that.. sorry.

Try this maybe:

PHP:

$sign->getZ() + 1 || $sign->getZ() - 1;

Doesn't || means OR? If it is, it would be better if you use XOR.

Trygonometry.
You can use functionas Block::getSide()

Teach me how