The things you learn: Dutch bottle scrapers
A utensil that’s apparently ubiquitous in the Netherlands yet unknown outside the country: the bottle scraper (flessenschraper/flessenlikker).
Useful for extracting the last bits of vla (which is more viscous than milk) from the bottles it was traditionally sold in; modern versions of the scraper apparently have not only a rounded edge useful for bottles but also a straight edge with two right angles useful for the cartons that vla tends to be sold in these days.