The Thickness Gauge is used to determine if the aggregate particles are to be considered as flaky, i.e. their thickness is less than 0.6 of their nominal size. The aggregate to be classified is separated into seven sieve fractions from 6.3 to 63 mm, and each fraction is examined separately. The Length Gauge (Elongation Index BS), is used to measure the elongation index of aggregates. When the length of the particle is more than 1.8 of the midsize of the sieve fraction, it is considered elongated. The aggregate to be classified is separated into six sieve fractions from 6.3 to 50 mm and each fraction is examined separately.
