a few, two, etc. bricks short of a load
a few bricks shy/short of a load
A pejorative phrase meaning not very intelligent or of questionable mental capacity. It can appear in many different forms and variations (for example: a few sandwiches short of a picnic, a few cards shy of a full deck, etc.). He says he's going to start a business selling bees as pets—I think he may be a few bricks shy of a load.
a few, two, etc. ˌbricks short of a ˈload(also a few, two, etc. ˌsandwiches short of a ˈpicnic) (informal) (of a person) not very intelligent; slightly crazy: If you ask me, I think he must be one or two sandwiches short of a picnic! OPPOSITE: all there
The structure a few, two, etc....short of a(n)... is often used to make new idioms, for example a few cards short of a deck, a few letters short of an alphabet.