Explanations:
The frog is provided in bricks for mainly two purposes– 1. It serves as a key of mortar when other bricks are placed over it. 2. It indicates the trade name of the manufacturer. • According to ISI specification, size of the brick should be 190 mm × 90 mm × 90 mm and the depth of the frog should be between 10 to 20 mm length and width of frog should be 100 mm and 40 mm respectively. • A good brick should be uniform in size and should have rectangular plane surfaces with parallel sides and sharp straight right angled edges. • An ordinary rectangular brick normally has rectangular (10 cm × 4 cm × 1 cm) frog is provided as well as oval frog (6 cm × 4 cm × 2 cm) is also provided.