18 were carved cherubim and palm trees. Palm trees alternated with cherubim. Each cherub had two faces:

Read Ezekiel 41:18 Using Other Translations

And it was made with cherubims and palm trees, so that a palm tree was between a cherub and a cherub; and every cherub had two faces;
It was carved of cherubim and palm trees, a palm tree between cherub and cherub. Every cherub had two faces:
All the walls were decorated with carvings of cherubim, each with two faces, and there was a carving of a palm tree between each of the cherubim.