门很坚固
mén hěn jiān gù
The door is very sturdy.
墙很坚固
qiáng hěn jiān gù
The wall is very solid.
基础很坚固
jī chǔ hěn jiān gù
The foundation is very stable.
他们的合作很坚固
tā men de hé zuò hěn jiān gù
Their cooperation is very solid.
