Put the hammer down

To put or drop the hammer down, sometimes with the word ‘down’ omitted, has come to mean to exert maximum pressure or attention to some task or other. It can also mean to go flat out at great or maximum speed, either in a motor car, or a bicycle, or on foot. It is first attested from truck driver slang in America in the early 1960s, where the ‘hammer’ is slang for the accelerator.