Snap is activated only if the target object is not on grid.

X-position

Moves the replacement object horizontally to the closest column guide, left or right of the object, whatever is closer.

Y-position

Moves the replacement object vertically to the closest module guide, up or down of the object, whatever is closer.

Width

Changes the width of the replacement object so it aligns to the closest column guide.

Height

Changes the height of the replacement object so it aligns to the closest module guide.