Bit of a random one! - building out a rolling cart with gridfinity next to my desk and wanted an area to put my coffee - I had an old 100mm square coaster and thought "why not?"

(Unintentional advert for Hallmark engraving and signs - if they're still around, check them out for quality engraving work)

Originally designed as a 3x3, but redesigned to save filament as one corner piece that can be printed four times to support a solid coaster.

Works well, and has given me some ideas for organising larger items in gridfinity without using a ton of filament :)