The next step was to screw the semaphores in and to connect them up.
But getting screws for the job proves difficult. The smallest screw I could find (even at a usually well assorted ironmonger) is 2.5×12mm. And I need 1.5×10mm (or, at most, 2×12mm) screws…
A couple of weeks later, I found them in small model aeroplane shop in my neighbourhood. While I was not able to get hold of wood screws that short I could buy a set of 2mm bolts. And with a small drill I was finally able to fix all semaphores. Just their cabling is missing – but that should not take too long.