If you need to use the same object snap repeatedly, you can set it as a running object snap, which means it stays on until you turn it off. For example, you might set Center as a running object snap if you need to connect the centers of a series of circles with a line. As with single object snaps, the aperture, or target box, indicates that an object snap is on and identifies the selection area. You can change the size of the target box.
When you turn on multiple running object snaps, AutoCAD LT uses the object snap most appropriate to the object you select. If two potential snap points fall within the selection area, AutoCAD LT snaps to the eligible point closest to the center of the target box.