Jnlib layout files are used to define positions of elements on the screen. These files are BNCL, BNBL, and BNLL. They share a common header and coordinate structure. The header of these files is structured as:

Jnlib layout files use a common structure for storing coordinates. This allows for storing a coordinate relative to one of 9 points on the layout element. These take the following structure:

?? OO XXXXXXXXXXXX
|  |  |
|  |  +----------- The coordinate as a signed 12-bit integer.
|  +-------------- The origin. Can be 0 (left/top), 1 (center), or 2 (right/bottom).
+----------------- Unknown.

The origin position sets the position of the layout element with respect to one of 9 points on the element. These points are illustrated below: