Seven sandwiches short of a picnic.
~

A few crumbs short of a biscuit.
neuron impaired

A shingle short on the roof of life.
a bit slow

Three bangers short of a barbie.
dull-witted, slow.

Twenty cents short of a dollar.
not all there- crazy

Short of a sheet of bark.
weak of intellect

Few tiles short of a roof.
slow , not very quick

A few bricks shy of a full hod.
~

Ten thousand sheep short of a top paddock.
kind of slow, an idiot

She's two bob short of a pound.
A bit slow in the brain

He's a sandwich short of a picnic.
Not very intelligent

Few snags short of the barbie
not all there idiot (snags means sausages)