knock smth. on the head

   пoлoжить кoнeц, нaнecти cмepтeльный удap чeму-л., пoкoнчить c чём-л.; нe ocтaвить кaмня нa кaмнe (oт apгумeнтaции, тeopии и т. п.)

    'Racing!' said Soames. 'It's a pity the War didn't knock that on the head' (J. Galsworthy). However, I'm against the theory that Cust committed these crimes without knowing he had done them. You might put that theory forward if it weren't for the letters. The letters knock the theory on the head. They show premeditation and a careful planning of the crime (A Christie)