Sandwiches

[Unregistered]

Could you please explain the phrase
"two sandwiches short of a pic-nic".
Thanks very much

[RonBee]

Somebody who is two sandwiches short of a picnic is not playing with a full deck. He probably needs help figuring things out. He is not ready to play with the big kids. He lacks the cleverness to be able to appear to be clever. He is capable of getting lost in an elevator. He is easily fooled.

[Asyut]

"A few [items] short of a [collection]"
is a common way to label someone as a little stupid.
A few oranges short of a bushel
A few beers short of a six-pack