I bought this juice carton but I've never seen this type of opening in my life. I'm stumped.
Edit: omg I didn't even notice the "lift" sign, thanks everyone! I did it!
Exactly, lift what’s left in the picture and pull towards you. It will push a hole through the carton with the right part which you can push down to support the plastic a bit.
Note these cartons cannot be closed again. EDIT: they can at least partly, see below
Well, they can be closed in the sense of „no fly gets in“, but oxygen does. Not to mention that juice would definitely flood out if you lied this on the side.