Filler strips are used between kitchen cabinets or near a wall at the end of the cabinets to cover any gaps. The strips have the same finish as the rest of the cabinets. They are one to three inches wide and sometimes wider.
Prepare the Backerboard
Prepare your backer board, which is recommended only if your filler strip is wider than three inches. Install it before the final cabinet.
Place a straight edge across the space between the end wall and the face of the closest cabinet and mark the wall behind the straight edge. The end cabinet is not in place at this point to give you room to work. Draw a straight vertical line from the mark you just made going down the wall to the floor. This line will tell you where to align the front of the filler strip.
Place the front of the filler strip on your mark. Draw a line to represent the thickness of the filler strip behind the filler from the top to bottom of it, for the backer board placement. The backer board is usually only a few inches thick and serves to support a wider filler strip.
Attach backer board to the wall with drywall screws and a screw gun or finish nails and finish nailer. Plumb the backer board or make sure it is flat against the wall. Try to have the backer board fasten to a wall stud.
Trace a line from the bottom of the closest cabinet to the wall (this is the place where the end cabinet will go). Attach toekick backer block, which is a small square board attached to the floor to serve as backer or a stopper for toekick cover. Secure the toekick block (2 x 2 inch block of wood) to the floor by the front cabinet line (where the end cabinet will go) just behind the cabinet line next to the wall. Use finish nails and nailer (or drywall screws and screw gun).
Install Last Cabinet
Place your end or final cabinet in position and shim cabinet by placing small pieces of wood (shims) behind it if there are any gaps or it doesn't fit tight.
Level the cabinet and place more shims if needed.
Install the last cabinet using manufacturer's recommended method for your cabinet brand.
Measure Filler Board
Measure the gap between the wall and the end cabinet, near the top and bottom of the cabinet, once your last cabinet is placed.
Check the wall contour to determine if it is even. If your measurements for the top and bottom of cabinet to wall are the same, the wall contour is even. If so, mark your measurements on the filler strip and cut the wall filler with a table saw.
Scribe, or mark the wall if you have an irregular wall contour or if your measurements are different from the top and bottom of the cabinet to wall. Run a strip of masking tape from the top to the bottom of the front surface of the filler strip edge that needs cutting. This will make it easier to see your scribe mark and also protect the surface of the filler when cutting. Clamp the filler strip parallel to your end cabinet with uncut edge (with masking tape on it) closest to the cabinet. Use a compass to scribe the contour of the wall by running the opened compass along the uneven wall to transfer the measurements of the wall onto the filler strip. This traces a line on your masking tape of the uneven wall that you will use as a guide to cut so the filler strip will fit properly in between the end cabinet and wall.
Cut the wall filler using a table saw to your scribed marked width. Sand edges lightly, if they are rough, use a belt sander, once you have the correct size. Place filler in correct position and pre-drill holes (to prevent cracks in wood) from the inside edge of the end cabinet through to the filler strip. Three or four screws spaced out along the edge should be enough to hold the filler strip. Fasten with small drywall screws between the final cabinet and filler edge.
Tack your filler board to backer board (if used) with finish nails.