How do I create a 1px line in Interface Builder?

Question

Note, I\'m looking to make a 1px line, not a 1pt line. Meaning it should be 1px regardless of screen scale (so 0.5pt on Retina devices).

I can do this programmatica

Answer 1

EDIT: This answer was for @2x only devices. At that time @3x was not yet on the market!

Nowadays, @mdvs's answer seems to be the cleanest.

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Making 1px line in IB is hard even for retina-only devices. Finally I've achieved it using the User Defined Runtime Attributes.

Here's a screenshot for setting the Height Constraint to 0.5 px (which is 1px on retina devices).