A hole in an object such as a slab must be completely contained. The hole cannot touch the edge of the object or extend past the edge of the object.
To model expansion joints in a sidewalk, create a single section of sidewalk and then replicate it with small gaps in between each section.
There are several ways to move piers and pads; however, they must always be positioned under a wall. A pier or pad can only be moved away from the wall it is placed beneath if it is moved to another wall.