Lesson 2-1-16 - High F Natural
High F natural is one of the nine half-holed notes in the standard 25 notes for a Key of D Whistle, and one of the five high half-holed notes. As a result, you're unlikely to learn this note until you've mastered nearly all of the other notes.
It's made by covering the top four holes completely, half-covering the fifth hole, leaving the last hole uncovered, and blowing harder than you would for Low F natural.
I find that squashing the right middle finger up against the index finger and tilting the nail slightly towards the ceiling while pressing down hard gives the most control while playing this note, although this is quite hard to master, and needs practice.
As with all the half-holed notes, I'd recommend learning the full-holed notes first before trying them. There are fantastic whistle players out there who cannot play these notes with any degree of proficiency, and they still manage to play fine music.