A special WoW resource texture type used to help render border on frames.
An edge file is just a normal WoW texture image file (obeying the normal WoW file size rules), which will then be split horizontally by the UI engine into 8 equally sized slices (The actual file dimensions shouldn't matter as long as the width is a multiple of 8).
The slices are placed as follows (going from left to right)
- Left edge
- Right edge
- Top edge (Rotated 90 degrees Counterclockwise)
- Bottom edge (Rotated 90 degrees Counterclockwise)
- Top Left corner
- Top Right corner
- Bottom Left corner
- Bottom Right corner
The frame border is then made by repeating the edge images in between the four corner images.