Knock Down Meaning

(transitive, usually passive) To disassemble for shipment.

Example:   As I took the can off the shelf, I knocked down the one beside it.
  We knocked down the garden shed when we moved.
  The picture was knocked down for £50.
  They knocked it down by another £5, so we bought it.
To drink fast
  I love to go down the pub and knock down pints of lager.
  The furniture is shipped knocked down, so assembly is required.