Placing filler strips between cabinets or at the end near a wall helps fill gaps and gives them a more professional look. The strips are usually the same finish and material as the rest of the cabinets and can be 7.5 cm (3 inches) wide and sometimes larger. While installing these usually requires a lot of skill and precision-cutting, you'll have a successful project if you follow the correct procedures.
Prepare the backer board, if needed. Backer board is only used behind the wall filler if the filler is wider than 7.5 cm (3 inches). Backer board should be installed before the final cabinet.
Run a straight edge along the area between the wall and closest cabinet. Mark the wall behind the straight edge and draw a straight vertical line from the mark.
Align the front of the filler on the mark and draw a line behind the filler for the backer board position.
Attach the backer board to the wall with plasterboard screws and a screw gun or finish nails and a finish nailer, until it is plumb or flat against it. Make sure the backer board is fastened to a wall stud.
Attach a toekick backer block (as a backer for the toekick cover) to the floor by the front base cabinet line with plasterboard screws and a screw gun (or finish nails and nailer).
Shim the cabinet, if needed.
Level the cabinet.
Install the final cabinet using the manufacturer's recommended method.
Measure the gap between the wall by the top and bottom of the cabinet, once the final cabinet is installed.
Inspect the wall contour to make sure it's even, and if so, mark and cut the wall filler with a table saw.
Scribe the wall for an irregular wall contour. Run a strip of masking tape down the filler where the scribe mark will be as a guide and to protect the wall filler when cutting. Clamp the filler parallel to the final cabinet (or in front of it with the uncut edge parallel to the cabinet) and scribe the wall contour with a compass onto the filler surface.
Cut the wall filler with a table saw to the appropriate width of the scribed mark. Sand the edges lightly, if needed, with a belt sander, once you have the correct size. Put the filler in place and pre-drill holes and fasten between the final cabinet and filler edge, using small plasterboard screws.
Tack the wall filler to the backer board (if used) with finish nails.
Remember that scribing is only required if the wall surface is uneven or irregular and there are gaps when trying to fit the filler board. When making your cuts, cut carefully. It is easier to cut too little than to cut too much and have to buy another filler board. When sanding, sand lightly just to smooth off the edges.