Nouns ending in -ette are usually feminine.
The suffix often forms a diminutive.
Is serviette masculine or feminine?
laserviette
The rule behind it
99.3% of -ette nouns are feminine
In context
Puis-je avoir une serviette, s'il vous plaît ?
May I have a napkin, please?
La serviette n'était pas utile du tout.
The towel wasn't useful at all.
La serviette ne fut pas du tout utile.
The towel wasn't at all useful.