(as) sure as a gun American British informal
This expression has been replaced by the phrase "sure as shooting".
With absolute certainty; decisively
The sky is gray, it is sure as a gun raining torrentially.
Jenni is sure as a gun joining the concert tonight since her idol will perform there.
Being recruited in the marketing company she adored, as sure as a gun, she will work there in the long run.
Meaning absolutely certain or without a doubt
To be trustworthy, secure or firm.
Another way to say "absolutely", "definitely" or "for sure"
That's absolutely right.
Totally certain.
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.