I have pasted a link to an Illustrator file below where I am trying use the pattern on top to cut out the blue rectangle below. So the outcome is that what you see as black becomes transparent (cut-out) and what is blue is left filled in, to give a stencil like effect.
I’ve played with expanding the pattern etc but getting confused how to work with all the compound paths that are created after that step.
Thank you for any help in advance.
You are so close…
Select your rectangle with the pattern fill (not the blue rectangle)
Go Object> Expand and click OK
Select All and go to Window> Pathfinder
Click the Merge button in the Panel (3rd from left on the bottom row))
Select only the Compound Path which is the black lines (it should be the top Compound Path in the Group that is made from the Pathfinder step) and click Delete