Straight as a whistle

To go very straight.
Similar to 'dead-on'

A skudded that baw as straight as a whistle

by Definitely Not Monty July 3, 2020

Straight as a whistle

Not actually straight, referencing the curved end of standard whistles.

- I'm straight as a whistle!

- But whistles aren't straight?
- Correct.

by silkyshush January 10, 2021