You could check to see if the “P trap” has removable fittings on each end, then it’s just like unthreading the coupling and clean out the obstruction. If not try the snake method already mentioned. It’s probably just hung up on some build up as the glass pieces should be fairly small to fit in the drain.
You could try using the plunger but make sure to disinfect first and then the sink after.
You could probably find a YouTube video to demonstrate, it should be a relatively easy fix.
Measuring tapes are more widely used by a massive margin. Folding rulers are rare I would say. That being said I have about half a dozen, but all were provided by European manufacturers. I don’t think I’ve ever seen one in a hardware store but I think you can get them on Amazon fairly readily.
That being said, maybe they are more popular than I think as I never need to buy one.
And fascist don’t forget that part!
It’s quite sad to watch the decline of America.