not know B from a battledore

not know B from a battledore

To be really stupid, or perhaps illiterate. The now-outdated term "battledore" was often used in reference to a children's primer. It was likely used in this phrase simply for the sake of alliteration. How do you manage to burn pasta? It's like you don't know B from a battledore.
See also: know, not
Farlex Dictionary of Idioms.
See also:
  • come in
  • come in a certain position
  • come on in
  • enlist in
  • enlist in (something)
  • be (flat) on (one's) back
  • (Is) that everything?
  • (Is) this taken?
  • flat on (one's) back
  • flat on back