Locate and mark the studs inside of the knee wall with a stud finder and a pencil. Mounting the corbels directly to a stud allows it to support the most weight.
Measure the distance between the studs with a tape measure to determine the desired spacing. It is not necessary to mount a corbel on each stud. Three corbels, spaced evenly apart should support a countertop of up to 8-feet. It is important to note that larger countertops and those made of heavier material such as granite might require additional corbels.
Place a corbel in one of the selected locations over a stud and slide it up until it is flush with the bottom of the countertop. If necessary, use a small level to straighten the corbel before installing.
Install wood screws of sufficient length through the pre-drilled holes in the corbel using a screw gun to secure the corbel to the wall stud. Repeat this step for the remaining corbels.
Caulk around the edges at the top of the corbel where it meets the bottom of the countertop with silicone adhesive for additional support.