Apply a small amount of thinset mortar to the tip of a trowel. Carefully apply the mortar to the corners of the countertop where the V-caps will go. Smooth the mortar with the trowel, being careful not to bump the other tiles.
Apply a small amount of thinset mortar onto the back of each V-cap and smooth it out with your finger or the tip of the trowel.
Line up one of the V-caps with the corner of the counter, ensuring the top of the V-cap sits flat on the counter. Ensure the side of the cap hugs the edges of the counter.
Hold the V-cap in place for a few minutes to allow the mortar to take hold. Repeat Steps 1 through 3 for each additional V-cap.
Allow the mortar to dry overnight. Apply a thin amount of grout between the edges of the V-caps and the surrounding tiles.