I use these in the household toilet bowl as a substitute refill for the Harpic (and other brands), toilet 'cage' hangers that just go over the edge of the porcelain and catch the flush of water round the upper rim of the bowl. I have four of these little beauties hanging on in there, and these little blocks work nicely to create a fresh clean bubbly flush and fragrance, and they last for a long time. These hanger things used to be more common in the supermarket, and the refills were often a little hard to come by. But while the plastic hangers practically last forever, the blocks often did not, so these are a splendid refill. Not the standard usage, but there you go.