WDM-INOP

What does "INOP" in rectangle mean in the wiring diagram?

Would like to see it here to be for sure but to me sounds like the triangle (a flag) is showing that a component is inop at time of installation. You will see these or similar alot of STC or engineering drawings for new installations as components will he installed wired up tested but then be INOP or unusable until final approval from authorities. Then revision will be made and inop flag removed.

Could be other reasons but that's the only one I can think of.

See attached print.

Mark's note: I cannot show a complete Boeing print on the site. I've removed yours and inserted two smaller screenshots.....
  
     
     
 

Yeah it's disabled inop because C/B collared.

Never personally seen a 737 with airstairs i have seen some BBJ and other wide body equipped with them as option or Modification after the fact.

Probably disabled because they no longer need it or want to maintain it.

Does it mean the corresponding wires are capped?

No the C/B are pulled with a permanent collar usually red.

How can I verify that the corresponding wire is capped off?

The print doesn't ask for it to be capped off. Just the collar.

A capped wire is shown as.....
  
     
 

Would you mind spelling out why WDM asks for INOP label whereas the wires are not capped off and so the airstair may be serviceable.

With the diagram you have shown the airstairs are deactivated most likley by operator request. Either they aren't using them to costly to maintain or any combination of those to.

Deactivation through pulling the CB and applying permanent collar is much easier(cheaper) for MX and also makes reactivation easier if they decide to go that route.