put the tin hat on (something)

put the tin hat on (something)

To finalize, or finish off, or mark the end something, especially in a forceful, decisive, or dramatic way. Primarily heard in UK. What put the tin hat on it for me was his insistence that we maintain the same direction for the next financial year. I put in my resignation the very next day. The downgrading of the company's credit rating puts the tin hat on a disastrous year for their financial situation.
See also: hat, on, put, tin