[Boatanchors] a little OT: microphone booms

[W2HX]

Slightly ot.  I bought a mic boom for use with my boatanchors (tie in).  It is an older style probably from 50's or 60's. It is not, however, working the way I was expecting. I was expecting that the boom would allow me to position the mic for the best position after mounting it on the desk.  However, it seems to only be spring loaded but no way to "tighten" the position to keep it there. Here are some photos and a video of what I am talking about:

http://www.w2hx.com/x/Mic-boom/

Is anyone familiar with this style of boom and how it was meant to operate?
thanks


73 Eugene W2HX