But screw your courage to the sticking-place

From Shakespeare’s Macbeth, 1605:

LADY MACBETH
We fail!
But screw your courage to the sticking-place,
And we’ll not fail.

It is thought that Shakespeare was making the allusion to the screwing-up of the peg of a musical instrument until it becomes tightly fixed. If that is so then the phrase’s meaning is ‘keep screwing up your courage until it reaches the sticking place‘ not, as is usually thought ‘affix your courage to the sticking place‘.