[Zmagnette] door checks

[Steven Trovato]

Does anyone know how the door checks work?  These are the things that 
keep the door from opening too far.  I see how a metal bar stops the 
door, and I see that there is a sort of a cushion piece that softens 
the impact at the end of travel.  The door check is also responsible 
for keeping the door in the open position.  How does it do that?  I'm 
trying to understand the mechanism, so I can decide if I should just 
bathe it in lube while I'm in there working on the window.  Thanks.

-Steve T.