lay down a keel

例句：

1. 1. The ship was laid down on the seabed with great effort.
   这艘船在海底被艰难地安放了。
2. 2. The construction of the bridge was laid down in stages.
   桥梁的建设分阶段进行。
3. 3. The company laid down its roots in the city and began to grow.
   该公司在城市扎根并开始发展壮大。