Handy corner piece for perfect finishing of protruding corners. If you use 1 cm joints, you will require 35 corner pieces if a corner is 2.60 cm high. Brick height 6.5 cm + 1 cm joint = 7.5 cm. 2.60 divided by 7.5 = 35 pieces. The surface area of a corner piece (internal dimension long side (18 cm) plus short side (5 cm) = 23 cm x 6.5 cm high = 0.015 surface area per corner piece. If you have 35 corner pieces, you can cover 35 x 0.015 = 0.52 m2.