To model expansion joints in a sidewalk, create a single section of sidewalk, then replicate it with small gaps in between each section.
A hole in an object, such as a slab, must be completely contained. The hole cannot touch the edge of the slab or extend past the edge of the slab.
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.