HINNO double fingered pleat hook. Various manufacturers make their own versions of this small pleat hook including Silent Gliss who’s version is almost identical. Because of the small size these pleat hooks are very often found on installations on boats, ships, caravans, mini buses, camper vans, trucks etc.
NOTE sold in quantities of 1, photo for illustration.
Several other companies make similar double hooks for pleats, although they are all slightly different. The photos below show comparisons from different angles.
HINNO Double Fingered Pleat Hook comparison
There is one more variant that I know of, though it is slightly larger than those in the comparisons and that is the Regency Pleat Curtain Hook