Wörterbuch (en): Hairline crack / Hairline fracture
de:
Haarriss (m)
fr:
Fissure capillaire (f) / Fendilles (f.pl)
it:
Fessure (f.pl) / Crepa dell'attaccatura dei capelli
es:
Fisura delgada (f) / Fisura muy fina (f)
Cracks up to 0.2 mm wide. Repairing hairline cracks is relatively easy because the damage is not of a structural or static nature.