RichThesaurus
one brick short of a full load
vs
thick as two short planks
one brick short of a full load
adj
Stupid.
Not mentally sound; insane.
thick as two short planks
adj
Very stupid.
How often have the words
one brick short of a full load
and
thick as two short planks
occurred in a corpus of books?
(source:
Google Ngram Viewer
)