磕头如捣蒜

kè tóu rú dǎo suàn

lit. to kowtow like grinding garlic (idiom)

fig. to pound the ground with one's head

磕

kè

variant of 嗑[ke4]

头

tóu

head

如

rú

as

捣

dǎo

to pound

蒜

suàn

garlic