Razor baseplate, clarified
A three-piece safety razor comprises a handle, a baseplate, and a cap. The orientation of two is obvious: the cap has a threaded stud and the handle as a tapped receptacle for the stud: the handle and cap are screwed together, with the baseplate (holding a double-edged razor blade) squeezed between.
So the baseplate is the only piece with a possibly ambiguous orientation, and a few beginners find that they’ve attempted their first shave with the baseplate upside down (which doesn’t work). In the next edition, I’m going to include this photo and explanation:
The two baseplates are both from Edwin Jagger/Mühle razors of recent manufacture: this is the new head. The baseplate at the bottom is upside down: the blade goes on the other side; the baseplate at the top is rightside up: you just put the blade atop the side with the scalloped edges and the cap goes on top of that. (The actual process is to put the blade on the cap, then place the baseplate on top of that, with the scalloped edge facing the cap: it’s easier to load the cap since the cap has the two blade-alignment studs. Some razors have those two studs on the baseplate, in which case you load the baseplate and then put the cap on that.)