Use these options to set what happens when you select
.Sets the Grid U and Grid V options to common square texture sizes.
Change the Grid U and Grid V sliders or enter values to use a different or non-square size.
The number of grid lines horizontally (in the U dimension of texture space).
The number of grid lines vertically (in the V dimension of texture space).
Snaps UVs to the nearest grid intersection.
Snaps UVs to the nearest midpoint between grid lines.