Telplin

And each day of the Valar in Aman contained twelve hours, and ended with the second mingling of the lights, in which Laurelin was waning but Telperion was waxing.
— The Silmarillion, Ch 1, Of the Beginning of Days

Telplin helps F# users to generate matching signature files for implementation files.
It uses the F# compiler and Fantomas to achieve this.