To knock down is to demolish, or to strike to the ground. Knock down the wall.
It also means to reduce a price, which is where a knock-down price comes from. To knock down a wall in a house needs to be checked, since some are holding the upstairs up.
1phraseknock downTo demolish, or to strike to the ground.
“They wanted to knock down the wall between the two rooms.”
knock down is a phrase.
Practised in Phrasal Verbs