What trousers is made of

The trousers of nomads.

Trouser legs — has part. Two legs.
Waistband — has part. The upper edge.
Zip — has part. A fastener.
Button — has part. The waistband button.
Needle — uses. Trousers were sewn with a needle.
Wool — is made of. The oldest trousers (Yanghai) were sewn from wool.