How to lubricate your cart wheels
The black slug Arion ater enjoying life on Forvie Moor.
Believe it or not black slugs were once used to lubricate the wheel bearings of wooden carts in rural Sweden!
The traditional way to lubricate wooden axle-trees on the old wooden
carriers in pre-industrial Sweden was with tar, sometimes mixed with lard from swine or cattle, cod livers and raw eggs. Sometimes other substances were used, such as frogs, earthworms and black slugs!
Information from: Svanberg I. (2006). "Blacks slugs (Arion ater) as grease: a case study of technical use of Gastropods in Pre-industrial Sweden". Journal of Ethnobiology 26(2): 299–309.