@garage sale GT (and onespeedbiker),
by "turn the nut in the other direction" I was assuming you meant "turn the nut counterclockwise relative to the bolt." You may have meant re-positioning it?

@onespeedbiker - this is a $20 made-in-India knockoff of a Brooks, and did not comes with a manual. Where did you find webshots of the tension mechanism of this RBR saddle? (seriously, I'm interested, as I've seen nothing about how their mechanism is supposed to work. That's why I started this thread)

Again, turning the bolt with a screwdriver doesn't do anything to change tension because the bolt will just thread through the nut, and the threaded hole in the curved plate attached to the rails, at the same rate. To move the nosepiece you need to hold the bolt from turning, and turn the nut relative to the bolt.

@Slaninar - are you suggesting the curved-head end of the machine screw at the nose of the saddle, or behind the curved plate that attaches to the front of the saddle rails? Note that in the latter case, the machine screw would need to be threaded along its entire length.