Planet Quark

In QuarkXPress, a line will snap to a guide at the line’s center, rather than at the edge of its stroke. For thick rules, this can be either Good or Bad. To snap the line using the edge of its stroke, select another object along with it before dragging both items.
(Trick: create a temporary item, then delete it after moving the line.)

The opposite behavior occurs when moving a Bézier path to a guide: the edge of its stroke snaps to the guide. To force the center of the path itself to snap, double-click one of its anchor points and then drag that anchor point to the guide. The entire path will move as you drag.