When you pay good money for custom kitchen cabinets, the only thing that remains is choosing the style of installation. What you need to know here is that cabinets are either installed flush to the wall with no back panel, or the cabinets have a back panel that is then mounted to the wall. You will need to choose one of these two installation styles, and there are reasons why your choice matters.
Flush to the Wall
If you decide not to mount a panel to the wall and have it double as the back of each cabinet, then you are mounting the cabinets flush to the wall. The wall itself becomes the back of the cabinet, and if you were to remove your cabinets in the future, they would not have any backs because the kitchen walls are the backs. To get the side and back edges of the cabinets to adhere to the wall, special epoxies or glues are used, and sometimes the cabinet maker may even create notches in the back edges to "hang" the cabinets on screws that are already drilled into the studs of the walls.
People choose this option to save money on cabinet making supplies. The cabinet maker does not have to buy a ton of extra wood to make the backs of the cabinets. Therefore, the cost is not passed on to the customers. On the flip side, the cabinets and floors all have to be level enough to make this work, otherwise, the cabinet maker has to insert several wedges to make the cabinets level and flush to the walls when they otherwise would be leaning forward on slanted floors and unable to be flush with the walls. Additionally, you will need to make sure that the walls behind your cabinets are painted the same color as the rest of the visible kitchen walls, or you will open your cabinets to see the old wall color at the backs of your cabinets.
Backed (No Wall)
The cabinet maker makes complete cabinets with backs. He or she is then able to mount the cabinets to the wall by drilling screws or driving nails through the backs of the cabinets into the walls. They are more securely attached and will hold to the walls for years to come. The cabinets mounted higher on the walls and close to the ceiling will also stay put because the full cabinet backs keep the cabinets in place as the cabinet maker installs them.